Don ' t Step on the Grass ( comic story ) Don ' t Step on the Grass was the four part story arc begun in " Doctor Who " ( 2009 ) # 9 . It was the first story in the series to be set on modern Earth , and featured the return of newly - married Martha Jones , Captain Magambo and UNIT . Summary . When the Doctor is called back to modern - day London by Martha Jones and UNIT , the last thing he expects are the Enochian Angels of Elizabethan magician John Dee , the secret underground library of Greenwich Park , and an army of angry living trees ! Plot . The Doctor was summoned to Greenwich Park by Martha and Captain Magambo who claimed that the trees were moving , three people were ingested by them and the trunks were marked with Enochian symbols , a language invented by mathematician and magician John Dee to converse with angels . The Doctor realises the " angels " were trapped beneath the observatory for four hundred years , but emerged through the trees in the park . While he sent Martha and Matthew to investigate Crane ' s house , the Doctor , Emily and gardener Mr Crane headed into the passages beneath the park to communicate with the " angels " , in actual fact aliens waiting in suspended animation for the Doctor to come and take them home . With a UNIT soldier , Martha and Matthew searched Mr Crane ' s house . Matthew discovered a sketch of the Advocate , but the soldier took it from him , urging caution in his dealings with the Doctor . The soldier was really the Gizou in disguise . Martha , meanwhile , discovered an alien dossier on the Doctor and realised he was set up . Believing the Enochai ' s story , the Doctor set them free , but it was a trick . John Dee trapped them , but they became free to take over all of the trees and claim the Earth . The Enochia realised the Doctor didn ' t remove the forcefield trapping it and ordered Crane to shoot Emily . The Doctor and Emily escaped but plunged down a hidden shaft into an ancient cavern where they discovered a stripped down colony ship containing thousands of Enochians in stasis . A holographic projection of John Dee informed them that the Enochians were energy beings who planned conquest . Emily escaped to the surface but Crane caught the Doctor and the Enochian ordered his imprisonment . The Advocate arrived and opened the stasis pods , releasing the Enochia . The trees drove UNIT back , but the situation became even worse as the Enochia flooded out of the ground . The angels trapped Central London in a forcefield . A battle with UNIT began , leaving UNIT seriously outgunned . The Doctor spoke to one of the angels and realised it was the Gizou in disguise . The Gizou revealed that the whole scheme was a set - up . The Advocate appeared to Martha and the trapped humans and proposed a way of ending the crisis , by striking at the Enochian ship . Crane , who overheard the Gizou , rescued the Doctor . Martha , meanwhile , escaped the bunker , found Emily and , with the help of the Knights Arboretum , a select group of gardeners of which Crane was once a member , was reunited with the Doctor . Returning to the bunker , the Doctor confronted the Advocate , but Magambo refused to allow him time to develop an alternative solution to the Enochia threat and insisted on following the Advocate ' s plan . She arrested the Doctor . With the help of the Knights Arboretum , Martha and Emily rescued the Doctor . Mr Crane , meanwhile , returned to the ship on a suicide mission to destroy it . The Doctor arrived and launched the ship into space , which drew all the energy creatures up with it . The Advocate ' s bomb was no longer needed , but the countdown was accidentally started . Mr Crane spotted it in the nick of time , but if he rose his finger from the button , the ship would explode . The Doctor could do nothing to save him so escaped using a pair of angel wings . The Advocate used Crane ' s death to finally destroy Matthew ' s faith in the Doctor and Matthew elected to instead travel with the Advocate .