The Return of Doctor Mysterio ( TV story ) The Return of Doctor Mysterio was the 2016 " Doctor Who " Christmas special . It was the show ' s twelfth Christmas special since its revival , and the third Christmas special starring Peter Capaldi as the Twelfth Doctor . It saw the return of Nardole from the previous Christmas special , this time as the Doctor ' s companion . The circumstances leading to Nardole ' s return were not explained until 2017 ' s " Extremis " . Due to the delay of Series 10 ' s broadcast , this was the only episode to be aired in 2016 , making the year notable for having the fewest episodes broadcast , discounting the show ' s cancellation period and TV : Doctor Who . The following day , " The Return of Doctor Mysterio " was granted a sequel entitled " Ghost Stories " . This story made the Ghost , Lucy and baby Jennifer all companions of the Twelfth Doctor . Steven Moffat was hugely influenced by the comic book s he loved as a child in writing this episode — particularly Clark Kent , Moffat ' s favourite superhero , both then and now . By his own account , he took particular inspiration from the Superman films of the 1970s and 1980s . Though clearly humorous in tone , " The Return of Doctor Mysterio " explores many common superhero themes , such as the hero ' s secret identity , his origin story , and a love triangle involving both the hero and the man behind the mask . Synopsis . The Doctor once more faces off with an alien species that wishes to conquer the planet : Shoal of the Winter Harmony . This time , he has more backup than usual ; however , this help was a little twist to it : it ' s a superhero called the Ghost . Plot . On Christmas Eve , 1990s , New York City , a boy named Grant wakes up during the middle of the night to find the Doctor swinging from his ankles in front of his bedroom window . He asks to be let in , and Grant goes to ask his mother ; Grant lets the Doctor in . Confused , the Doctor asks what Grant told his mother ; Grant said there was " an old guy " at the window . Realising that Grant has mistaken him for Santa , the Doctor gives a " ho ho ho . " Reading through some comics Grant has , the Doctor is given milk and cookies . He draws Grant ' s attention to a " Superman " comic ; the Doctor points out how ridiculous it is that no - one can tell that Clark Kent and Superman are the same person just because of a pair of glasses . They head to the roof , with the Doctor now confused about " Spider - Man " , whom Grant tells the origin story of ; however , the Doctor believes getting bitten by a radioactive spider would result in radiation poisoning . The Doctor reveals a device he is unable to describe in simpler terms than a " time distortion equaliser thingy " . There has been a lot of temporal problems in New York , and he ' s trying to straighten them out . Hearing Grant cough , the Doctor hands him a glass of water from his pocket ; when asked how that ' s possible , the Doctor states he has " skills . " He also hands him a red gem . Grant asks why the Doctor is working on the device ; he thought he was setting a trap . The Doctor explains that he accidentally fell into a trap he set to protect from people who would mistake it for a Christmas tree and steal it ; it ' s science , it ' s supposed to look like something somebody already knows about . When asked for his name , the Doctor states that he is the original Doctor that started the title ; " now anyone who wants to be called clever , calls them - self a doctor . " Amused , Grant tells the Doctor that if he was a comic book character , he ' d be called " Doctor Mysterio " . The Doctor is likewise impressed with the title , saying it himself in a dramatic voice . He asks Grant if he wants to turn on the machine , showing him a slot for a gem stone he handed him . He explains that it ' s called the Hazandra or the " Ghost of Love and Wishes " . It takes power from the nearest star to make the wisher ' s dream come true . The Doctor intructs Grant to put the gemstone inside the device . However , Grant reveals that he thought the gem was medicine for his cough and swallowed it . Grant begins to levitate , as the Doctor tries getting Grant to calm down , but the boy does the opposite , launching them into the air . Years later , a man awakens to the sound of crying baby . He rushes out of bed and tends to the little girl . He calls the mother , whom works for as a nanny , assuring her that her daughter is safe and sound . A red glow from his chest reveals him to be Grant as an adult . On top of the Empire State Building , Grant asks what is happening , and the Doctor tells him that the gem has granted what it thinks he wants : superpower s . Sometime later , a conference is held at Harmony Shoal , where Mr . Brock is questioned by Lucy Fletcher as where the benefactors for the organization are . Brock jokes that he killed them all and buried them in his backyard . Nardole asks where the little boys ' room is , but becomes confused by the American terminology . Brock is approached by Dr . Sim , who tells him something is wrong . He tells Sim to meet him at midnight . Lucy speaks to a woman on the cleaning staff at the same time . Come midnight , Dr . Sim leads Brock to a vault where brains are being held ; unbeknownst to them , Lucy has followed , having disguised herself as a janitor . Brock tells Sim that he knows that the brains were donated by the benefactors for a secret project that even he is not allowed to know ; Dr . Sim then tells him that there are more brains in there despite no deliveries being made to Harmony Shoal . Outside the vault , Lucy hears someone eating and turns to find the Doctor next to her . The Doctor tells her he broke in too , and has brought sushi ; according to him , bringing a snack is the mark of a pro . Told to tap the glass of a container , Brock complies and suddenly the brain inside sprouts eyes . Scared , Brock punches Sim in the face , dislodging the right side of his face , and spilling some blue liquid ; Sim puts his head back in place , showing he ' s not human . Sim points to tank without liquid , which he says is the brain of the real Sim ; they switched " containers " . Brock asks what happened , and Sim states it ' s the same thing that ' s about to happen to him : " a change of mind . " Surgeons emerge from hidden compartments and surround Brock , and Sim locks the screaming man inside of the vault . The Doctor and Lucy run away , with her revealing her true identity to him ; after her shock , the Doctor jokes it ' s spooky how that happens . When asked for his identity , the Doctor calls himself " Dan Dangerous of Scotland Yard . " He looks at a map showing where Harmony Shoal has set up shop , which is every capital city on the planet . Nardole arrives , noting that New York is not a capital city . Annoyed , the Doctor tells Nardole that he ' s not there to point out his mistakes ; he then realises Nardole was right . Sim confronts them with a gun , intending to kill them as security might leave them alive ; it would leave too many questions . However , the Doctor makes the situation a stalemate as no - one will believe he shot three people in the back in self - defence , making Nardole and Lucy turn their backs to Sim with him . The situation gets stranger as they hear knocking on the window of the 100th floor . Lucy turns around in shock ; it ' s the Ghost , a superhero vigilante . The Ghost snaps his fingers and the window shatters ; Sim is impressed , as that window was designed to withstand the force of four nuclear bombs . Sim shoots the Ghost , but the bullets fly off of him ; the Ghost picks up Sim and tosses him into the map , stating he doesn ' t like causing long - term harm , but moderate harm is fine with him . He reveals that he knows Lucy ' s work for the " Daily Chronicle " , stating it ' s opinions are too biased ; she says she ' ll have a word with her boss . The Ghost asks about the Doctor and Nardole , to which the Ghost and Doctor exchange greetings that seem to identify themselves to each other . Asking Lucy if she needs a lift , the Ghost carries her out the window and flies into the sky . Heading to the window , the Doctor scowls after the Ghost , muttering " Grant . " In the past , on top of the building , the Doctor tells Grant that once the gem is gone from his body , his powers would go away , and makes him promise to never use his powers . The Ghost drops Lucy off , before noticing a monitor flashing on his belt . She jokingly asks if the " Bat signal " was an app now , before the Ghost flies off . The Ghost returns home , changing out of his uniform and back into his civilian clothes . He heads to the nursery , where he finds the Doctor cradling the baby , revealing that he tracked him by the gem fused to him . He also states that no superhero should leave a baby unattended ; Grant defends this as being able to be back faster than most parents can get to their children . The Doctor hands the baby to Grant , who reveals that he works as a nanny ; " got to make a buck somehow ; you don ' t get paid for saving the world . " The Doctor tells him that he thinks this is insane , and that ' s saying something coming from him . Nardole agrees , giving Grant a bottle for the baby . When asked how complicated he needs his life to be , Grant tells them less than it ' s about to as the mother of the child comes home : it ' s Lucy ! To keep Grant ' s identity a secret , the Doctor lies that he came to see how she was out of concern ; he got to Lucy ' s home before she did as a show of how concerned . Lucy accepts this , taking her daughter from Grant to put her back to sleep . The Doctor and Grant talk out on the fire escape . Grant has been in love with Lucy for 24 years , but never had the courage to confess to her . Then a few years back , they met again ; however , Grant ' s best friend was with him as well , and Lucy married him instead . However , once baby Jennifer came along , the father ran off with another woman ; Grant saw his chance to get close the Lucy again , becoming Jennifer ' s nanny . Amused , the Doctor points out Grant left the field open for others to try dating Lucy instead of him . The Doctor yells " Thank you ! " to sky , confusing Grant ; the Doctor states that he is thanking the universe for letting him meet someone who is worse at having a normal life than him . Hearing a siren , Grant takes off as the Ghost , leaving his glasses behind . Jennifer arrives moments later , asking the Doctor to come in for an interview . Using the squeaking noise of a Mr Huffle to torture the Doctor , Lucy gets him to confess to not working for any agencies and that the Ghost is not involved with the goings - on at Harmony Shoal . Catching sight of the Ghost on TV , the Doctor directs Lucy ' s attention to it ; the Ghost is being interviewed after helping stop a fire , telling the viewers to get smoke detectors for fire safety . Throughout the night , Grant takes off to help out . Lucy asks the Doctor if he can set up a meeting with the Ghost ; that moment , Grant calls her as the Ghost , setting up an interview the next night . Lucy catches Grant just after he hangs up , telling him that she needs him to watch Jennifer tomorrow ; Grant tries to weakly protest he has a date , but gives in . At Harmony Shoal , Sim greets his brother alien now in Brock ' s body . Despite Brock ' s skull being too small , Sim assures his brother that it will soften with wear . Sim shows him footage of the Ghost , who they believe is the finest " vehicle " available on the planet . They watch footage of the Doctor , who suddenly shouts " boo ! " It turns out he ' s right in the next room . The Doctor tells the duo that he offers them mercy , and won ' t follow them off the planet if they leave now . Taking this as a declaration of war , " Brock " opens his head and pulls out a gun . The Doctor tells them that they are just another attempted invasion of the planet , which will fail like all the others . The Doctor holds out a burger , which is confiscated by Sim . He reveals to them that he knows what their plan is : " unzip " the heads of the world leaders and place their alien comrades inside to conquer the world . However , the White House and the Kremlin would be the hardest places to break into due to " big fences , shouty people and cross dogs . " Sim reveals that they plan to make the leaders come running to them . The Doctor whistles , telling that it won ' t work . Sim wonders what he took from the Doctor , to which he is told it ' s a burger ; " Always carry a snack ; don ' t want it now . He ' s put me off my lunch . " The TARDIS materializes around the Doctor . Inside , the Doctor finds Nardole in robes from 12th century Constantinople ; it took a few hit - and - miss tries to pick up the Doctor . The Doctor asks for the facts , as he ' s saving the planet ; Nardole states that ' s what he does whenever the conversation becomes serious . Annoyed , the Doctor tells him to be nice to the person who " glued " his head back on . The Doctor pilots the TARDIS , landing " where they were , except not . " They head outside , into the Tokyo branch , where everyone is rushing out of the room . The Doctor explains that the flooded the downstairs with Pokemon . The Doctor searches the computers , finding a signal being sent into space . In New York , Grant wishes Lucy luck during her interview ; she ' s wearing a trench coat , stating that it ' s not a date . When she leaves , he changes into the Ghost and heads to the roof with a picnic . To his surprise , Lucy arrives in a red dress she keeps for dates . They start the informal interview , with Lucy asking some too - personal questions , such as the Ghost ' s sexuality . The conversation then goes to the superpowers that the Ghost has : he has flight , super - strength , invulnerability , super - hearing , pyrokinesis , and x - ray vision . When asked if x - ray vision is tempting , the Ghost states adolescence was difficult because of it . The Ghost tries revealing he ' s Grant to Lucy , who keeps looking in the wrong direction when his mask is off ; at the same time , Lucy reveals that she has been developing love towards Grant for always being there for her . When she turns back , the Ghost is masked again , telling her Grant must be admirable . In space , the TARDIS floats outside of a ship . The Doctor states that it ' s empty because the lights are off . They land inside , only to be attacked by androids that chase them to the bridge . Sim contacts them via the monitor , with the Doctor curious as to why the ship is pre - programmed to fall on New York . Sim states that when the time is right , they will drop the ship on New York , destroying everything except the Harmony Shoal building ; the world leaders will be tricked into thinking it ' s a safe haven and will get their brains replaced when they arrive . Seeing Sim just told him the time is wrong , the Doctor starts messing with the controls , which causes the ship to start falling towards Earth prematurely . Telling Nardole to say " Whee ! " , the Doctor smiles madly . Back in New York , Brock arrives at the rooftop to switch the Ghost ' s brain with an alien . Brock assures that the procedure will be painless , before telling the Ghost that he was talking to his fellow alien . The Ghost flies off , leaving Lucy behind on her suggestion . Brock threatens to bring Jennifer up as another hostage as Grant arrives as himself , telling Brock he ' s not going to touch that baby . With another hostage , Brock calls for the Ghost to come back or Lucy will die . Suddenly , everything begins shaking ; Brock looks up to the sky with horror , knowing it ' s his ship . Grant hears the Doctor ; he ' s using the sonic screwdriver to speak to him on a frequency only he can hear . The Doctor tells Grant to stop the ship or all life in New York will perish . Seeing he can ' t keep his dual life secret anymore , Grant tells Lucy to duck in his Ghost voice . Moments later , the Doctor shakes Nardole awake , telling him that a " shock - absorber " stopped the ship from blowing up . In the streets below , hundreds of people and police watch in amazement at the sight of a spaceship seemingly floating on a rooftop . On the roof , Grant tells Lucy he ' s sorry for not telling her , and to not slap him as he ' s holding a bomb . The TARDIS arrives , with a happy Doctor walking out , telling Brock they couldn ' t defeat Grant because he ' s left - handed ; Grant never let ' s go of the baby monitor in his right hand out of habit . Lucy tells Grant she preferred him in his superhero outfit , putting his glasses back on and kissing him . The joy from this has Grant flying off with her . The Doctor tells Grant to toss the ship into the sun when they ' re done . The Doctor reminds them that Jennifer is still in the apartment . Grant tosses the baby monitor to the Doctor , who hears Jennifer calling for something . Brock holds the Doctor at gunpoint , but is told to give up as a helicopter from UNIT has been sent to close their " head office " . Brock warns that Harmony Shoal ' s vengeance is known and feared throughout five galaxies , the Doctor scoffs at this , telling him Jennifer needs changing " You ' re not the only one whose full of it . " At Harmony Shoal office , the workers are being forced to leave the premises . A UNIT soldier comes upon Sim ' s body , which is now empty of the alien that replaced his brain . He asks the soldier who found it if the body was already like this ; he confirms it . The officer states that he ' ll put a call in to Osgood ; UNIT needs to be on alert for the presence of this rogue alien . The soldier turns around after his superior leaves , revealing a long scar on his face ; to avoid capture , Sim transferred himself into this soldier ' s body . Back at Lucy ' s apartment , she and Grant are now a couple ; both now happy to have someone who truly cares for them . Grant has also decided to quit being the Ghost unless he is absolutely needed again . The Doctor heads for the TARDIS after giving some bitter - sweet advice . When asked if there ' s something bothering him , Nardole explains the situation to them . The Doctor is still grieving for the loss of his beloved wife River Song ; for some time , the Doctor is going to be sad . However , Nardole is with him to make sure the Doctor doesn ' t stray from being who he really is . He leaves as well . Lucy turns to Grant , telling him he never really explained who the Doctor was . Smiling , Grant tells her " Doctor . . . Mysterio " . Having seemingly heard Grant , the Doctor smiles and starts up the TARDIS . The last scene of the episode show New York at night , as the TARDIS flies away , taking the Doctor and Nardole off to their next adventure . Crew . " to be added " Story notes . Production errors . " to be added " Filming locations . " to be added "