Partners in Crime ( TV story ) Partners in Crime was the first episode of the fourth series of " Doctor Who " . It marked the reappearance of Catherine Tate as new regular companion Donna Noble . It also saw Sylvia Noble and Wilfred Mott return , as Donna ' s family . Donna ' s father Geoff Noble , however , was implied to have died offscreen , following the sudden passing of actor Howard Attfield . Importantly , Rose Tyler made a cameo appearance , heralding her eventual return later in the season . This episode began the " Missing Planets Arc " , with it being mentioned that Adipose 3 had been lost . As a trick to the viewers , this was lamp - shaded by Matron Cofelia mistakenly believing the planet had been lost through political means , instead of it vanishing . As shown in the future story " Turn Left " , if the Doctor hadn ' t been around to prevent the " Titanic " from crashing into London , the Adipose would have chosen America instead . Worse , without anyone to prevent it , hundreds of people would have died . Synopsis . Donna Noble is determined to find the Tenth Doctor again — even if it means braving the villainous Miss Foster . But when the alien threat escalates out of control , can Donna find her Time Lord before the march of the Adipose begins at last ? Plot . Donna Noble , wearing a business suit , walks down a street on the way to Adipose Industries , as she is investigating them on their new weight - loss drug . Unknown to her , the Tenth Doctor is there for the exact same purpose . Both enter the Adipose offices through different entrances , and pass themselves off as employees of " Health and Safety " . Both the Doctor and Donna then crash a press conference held by Adipose Industries company manager Miss Foster , Donna sitting with the journalist s and the Doctor watching from the projection booth . A science reporter , Penny Carter of " The Observer " , asks what this drug does ; Miss Foster gives them a lecture on the science of the pill , and the meeting ends . The Doctor and Donna ask different employees for customer addresses ; Donna also takes a pill - shaped golden pendant — a free gift that comes with the pills . Throughout their time at Adipose , the Doctor and Donna have multiple near - misses . That night , Donna goes to the house of a woman named Stacy Campbell , who is preparing to go out on a date to dump her boyfriend now that her weight is going down so nicely — " I can do better than him now ! " Meanwhile , the Doctor interviews another valued customer , Roger Davey , about his use of the drug . Roger tells the Doctor that he knows he ' s lost a kilo of weight every night by 1 : 10 AM — that ' s when he ' s always woken up by his burglar alarm . The Doctor deduce s that this is because of his cat flap . Not only does it let things in , it lets them " out " too . As the Adipose slogan goes , " The fat just walks away . . . " Stacy goes to the bathroom , and Donna begins fiddling with her pendant ; the result is that a humanoid cute and tubby piece of fat forces itself out of Stacy ' s body . Donna , oblivious to what is occurring , then begins to investigate what ' s going on upstairs . Miss Foster is alerted that there has been an " unscheduled parthenogenesis " , and sends out a squad team to retrieve the new Adipose children . The Doctor is also alerted of the " birth " via a Y - shaped hand - held device and runs off down the street to track it . Once Stacy witnesses the Adipose child , Miss Foster activates " full parthenogenesis " , and Stacy ' s entire body is converted into numerous Adipose , leaving nothing but her clothing behind . Donna , who is now upstairs due to Stacy ' s screams , breaks into her bathroom just in time to see an Adipose " waving " to her as it jumps out the window . The Adipose Industries retrieval team scoops up the new Adipose and zooms off in their van , just missed by both the Doctor and Donna — who both give up , and head off in different directions , unaware they are only a few feet away from each other . Miss Foster goes through her CCTV records with her henchmen to find out just who " borrowed " a pendant , and spots her . Donna cancels Stacy ' s cab , and goes home , only to find her mother nagging at her about her unemployment . Donna sits at the table , ignoring her , as she tries to get over what she saw . She then goes to see her grandfather Wilfred Mott , who is up at the allotments stargazing . He says she looks like he ' s drifting , but she replies she ' s waiting for the right man — the Doctor . She says , " I met him just once . . . and then I let him fly away . " When Wilf urges her to look for him , Donna explains she has — but that he is nowhere . She asks him to keep an eye out for a certain blue box in the sky , and give her a shout if he finds it . Back in the TARDIS , the Doctor is examining his readings , talking to himself for a moment before remembering that Martha Jones has gone . He stands there in silence . The next day , despite protests from her mother , Donna takes the car to Adipose Industries , parking in an alleyway nearby . Shortly thereafter , the TARDIS materialise s immediately behind it . The Doctor and Donna hide in the building until after hours : the Doctor in a caretaker ' s cupboard , and Donna in the women ' s bathroom . Donna even goes so far to conceal herself as to pretend she is in church when her mother calls . Miss Foster suddenly stalks into the toilet s searching for the thief — and , much to Donna ' s surprise and relief , instead pulls out Penny Carter . Penny accuses Miss Foster of faking her results . As Penny is dragged to Miss Foster ' s office by her guards , Donna follows , peeking through the office door . The Doctor zips to the roof , fiddles with a window - cleaning crane and drops down to the office window . He watches the same event from the other side of the room . Unable to quite see what ' s going on , both pop their heads up — only to spot each other . They mouth frantic questions to each other while Donna does her best to mime her answers , all the while unaware that they are being watched by Miss Foster and everybody in her office . " Are we interrupting you ? " Donna runs , while the Doctor locks the door with his sonic screwdriver and raises his window - cleaning cradle to the roof , before racing to the stairs . The pair " finally " meet , but have to keep running and head back to the window - cleaning cradle to lower themselves down for a quick getaway . Before that , though , Donna explains how she went about searching for the Doctor . " ' Cause I thought , " How do you find the Doctor ? " And then I just thought , " Look for trouble , and then he ' ll turn up . " So I looked everywhere — you name it . UFO sightings , crop circle s , sea monsters — I looked , I found them all . Like that stuff about the bee s disappearing , I thought , " I bet he ' s connected . " ' Cause the thing is , Doctor , I believe it all now . You opened my eyes to all those amazing things out there . I believe them all . . . " However , even though the Doctor locks the pulley with his sonic screwdriver , Miss Foster has a sonic device of her own . She uses her sonic pen to cut one side of the supporting ropes , making Donna fall out and hanging to the broke rope . Before Miss Foster can cut the other one , the Doctor uses his sonic to knock the pen out of her hand and into his ; he uses it to open a window in below Donna and swings Donna inside before following after her . Intrigued someone with advanced technology has appeared , Miss Foster heads back in with her guards to confront the Doctor . Inside , the Doctor and Donna have arrived back in Miss Foster ' s office via the window . Out of breath from her screaming , Donna asks if she ' s right in thinking it ' s always like this with him around . The Doctor confirms with a smile and tells her it ' s time to run again . Donna rushes out as Penny , yells for answers ; the Doctor tells her that as a reporter , she should just invent a story , which is what people in her profession are good at . He unties her via the sonic , and runs out . However , Penny wastes the chance to flee by searching the office for evidence and is once more caught by Miss Foster and her guards . They tie her up again . Miss Foster , with her guards , finally catches up with the Doctor and Donna in the main office ; she notes that the Doctor must be an off - worlder due to his possession of sonic technology . The Doctor takes out the sonic pen he confiscated , noting that the design is sleeker than his sonic screwdriver . He asks for her real name , learning she is Matron Cofelia of the Five - Straighten Classabindi Nursery Fleet , Intergalactic Class , who has been hired by the Adiposian First Family to breed the next generation of the species from human s following the loss of their breeding planet . Donna wonders how losing a planet is even possible , but Cofelia dismisses it as politics she ' s not interested in . Cofelia ignores both Donna ' s protests about Stacy Campbell ' s death ( which she passes off as necessary to keep her presence secret ; she does feel bad that using an entire person ' s matter makes the Adipose born from them a little ill ) and the Doctor ' s that seeding a Level 5 planet is against galactic law . The Doctor decides to make a last request : does she know what happens if you use two sonic devices against each other ? Cofelia hasn ' t a clue ; " " Neither do I . Let ' s find out , shall we ? " " the Doctor smirks , pointing his sonic and her pen at each other and turning them on . The result is a painful sonic feedback , which stuns Cofelia and her guards . The Doctor grabs Donna ' s arm and pulls her away . Seeing that she cannot trap the Doctor , Cofelia fears that he might have alerted the Shadow Proclamation of her illegal actions ; she decides to call the Adipose to collect the children that have been born already . Seeing that keeping her cover will not last , Cofelia activate the inducer - they ' re going into premature labour . Down in the basement , the Doctor and Donna head into the cupboard where he hid all day , which has a secondary inducer hidden in the back . He quickly uses the fact that Miss Foster had wired the building to stun her guards . Donna then admits she was a fool to turn down the Doctor ' s original offer to travel with him , and asks if she can still come . Back in her office , Miss Foster activates the main inducer , which sends a signal to the free pendants that will trigger the Adipose birthing process in the company ' s one million customers , converting fat , bones and internal organs . . . and kill the hosts in the process . In a London wine bar , Sylvia Noble is having a girls ' night out ; one of them , Suzette Chambers , is an Adipose customer and " host " . Adipose start popping out of her , as well as out of Roger Davey back at his home . The Doctor manages to temporarily disable the process by unscrewing his Adipose capsule and attaching it to his inducer , but Miss Foster doubles the power . The Doctor begins to panic as he finds himself unable to stop the imminent deaths of a million people , but Donna offers him just what he needs : a second capsule , to block the increased signal . The second capsule overloads the system , and the Adipose clients return to normal ; but ten thousand Adipose have now been born , and are now making their way to Adipose Industries , causing traffic chaos throughout London . The ten thousand will have to do ; the nursery is coming . As a benefit , now that the truth about the Adipose weight loss program has been revealed , it ' s highly unlikely that humanity will welcome the Adipose back to Earth ; given that the spark of life could kill / convert them into Adipose . A gigantic nursery ship arrives over London to collect the babies ; while Sylvia gawps at it , Wilfred — the one who ' s always believed in extraterrestrial life — has his back turned towards his telescope in the other direction and his headphones on , and misses the whole thing . As it arrives , so does a signal from the Adiposian First Family , which the Doctor listens to via the secondary inducer ; he suddenly realises that it ' s no longer the human s , but Miss Foster who is now in serious trouble . The Doctor and Donna run onto the rooftop to watch several levitation beam s carry the Adipose babies up to the ship . Having already seen firsthand what the Doctor can do to even children who he feels are a threat ( the Racnoss children ) , she asks if he plans to blow the Adipose up too , but the Doctor refuses to harm them , as they ' re just children ; they can ' t help where they came from . Donna openly notes that that is a marked difference from the last time they were in that situation ; Martha ' s time with him seems to have changed him for the better . Smugly , the Doctor notes Martha fancied him ; " Mad Martha that one ; blind Martha ; charity Martha . " Donna jokes back to him . A child sees them as it ascends , waving at them . They wave back as the Doctor admits that as a weight loss plan , the Adipose birthing has its merits . They see Cofelia in another beam on her way up to the nursery ship . The Doctor pleads with her to get over to the roof ; the Adiposian First Family is aware that their actions are illegal , which means they need to get rid of their accomplice . Cofelia dismisses the threat because she ' s the nanny - but the Doctor remains worried , exclaiming , " Exactly ! Mum and Dad have got the kids now - they don ' t need the nanny " anymore ! " " At that moment , the levitation beam carrying Miss Foster is switched off , and Miss Foster , with just enough time to realise her fate , falls to her death as the Doctor comforts a terrified Donna . Immediately afterwards , the nursery ship leaves Earth . Back on the street the Doctor bins the sonic pen as Penny — tied again to her chair — flees the building , unable to cope with what ' s been happening ; comically running off still tied up , she yells that the two of them mad . Donna points out , " Some people just can ' t take it . " Donna promptly drags the Doctor off to the TARDIS — and is delighted to realise he parked just a few feet from her car ; it ' s just like destiny ! She promptly starts hauling a ridiculous amount of luggage out of the car boot and shoving it into the Doctor ' s arms , saying she ' s been ready to go for ages . The Doctor warns that it is a hard life but accepts her , saying that he just wants a mate . She misunderstands this to mean that he wants " " to " mate " , saying he ' s just a " long streak of nothing " and exclaiming , " Well , you ' re not mating with " me " , sunshine ! " The misunderstanding ( mostly ) resolved , Donna then calls her mum to say she ' s put the car keys in a certain bin for her to collect before asking a blonde girl to tell her mother , " That bin there " . While Donna returns to the TARDIS , the girl , a sad - looking Rose Tyler , walks off down the street and disappears into thin air . . . For her first trip , Donna tells the Doctor she wants to go " two and a half mile s , that way . " Back at the allotments , Wilf is still puttering about when he spots a certain blue box flying overhead . After first yelling for Donna , he takes a closer look through his telescope , and realises she ' s " in " the blue box , waving to him from the doorway — and so is the Doctor ! He starts whooping and dancing around in delight as the TARDIS spins away into space , happy she found what she was after : " Go on , girl ! Go on , get out there ! "