The TARDIS materialises on Dame Kelly Holmes Close on the day of the opening ceremony of the 2012 Olympic Games. The neighbourhood is preparing for the passing of the Olympic torch-bearer, but the mood has been destroyed by the inexplicable disappearances of several local children. A council worker, Kel, also mentions that cars have been breaking down momentarily all day. The Doctor and Rose investigate and realise that the source of the problems is a solitary 12-year old girl, Chloe Webber, who is able to cause people to disappear by drawing them. The Doctor hypnotises Chloe and finds that she is possessed by an immature Isolus, an alien life-form used to travelling through space with a family of billions, which has crashed its pod to Earth due to a solar flare. The Isolus relates and befriends Chloe, who had a troubled childhood, due to their mutual loneliness. The Isolus has also caused Chloe to draw a life-sized, exaggerated figure of her late, violent father, which briefly has become animated.
The Doctor explains that if they can find the Isolus pod and provide it power, the alien will leave Chloe. A frantic Chloe draws the TARDIS and the Doctor, trapping them both in one of her sketches, forcing Rose to try to find the pod herself. She rationalises that the pod is located on the hottest spot on the street, and is able to dig it up. With Chloe having already caused the entire crowd at the Olympic stadium to disappear and now intent on making everyone in the world disappear, Rose tries to find out how to power the pod. Thanks to visual indications from the Doctor's "picture", Rose understands that she needs to offer the pod heat mixed with emotional strength, which she does by throwing the pod towards the Olympic Torch. As the missing children start to reappear, Rose realises that so will the demon-like drawing that Chloe had made of her father. Rose and Chloe's mother are able to calm Chloe enough and the (unseen) monster disappears.
As the torch-bearer approaches the Olympic Stadium, he staggers, but the Doctor completes the run and lights the Olympic Flame, allowing the Isolus to peacefully leave Chloe's body and return home. As the Doctor and Rose walk off to watch the Games, Rose remarks that however hard they attempt, nothing will ever split the two of them up. However, the Doctor becomes uneasy and surmises that a storm is approaching.
The Shakespeare code
The episode begins with a young man romantically serenading a young woman, who watches from her balcony. Invited inside, the young man discovers that the woman, Lilith, is in fact a wrinkled hag; she introduces her two "mothers", Doomfinger and Bloodtide, who lunge, cackling, at the screaming youth, apparently devouring him.
Meanwhile, the TARDIS lands in Elizabethan London in 1599. The Doctor, who had promised to take Martha on one time-travelling trip, takes her to a performance of Love's Labours Lost at the Globe Theatre. At the end of the play, William Shakespeare announces a forthcoming sequel entitled Love's Labour's Won. Lilith, using a poppet, influences Shakespeare to declare that the new play will premiere the following evening.
The two go to The Elephant, the inn at which Shakespeare is staying. They chat with the playwright, who plans to finish writing the final scene of Love's Labour's Won that night. Lynley, Master of the Revels, demands to see the script before he allows the play to proceed. The trio of "witches" view the scene remotely by looking into a cauldron. Lilith, who works at the inn, secretly takes some of Lynley's hair and makes another poppet, which she plunges into a bucket of water, then stabs the doll in the chest, and Lynley collapses, dead. The Doctor calmly announces that Lynley has died of an imbalance of the humours, privately telling Martha that any other explanation would lead to panic about witchcraft. But when Martha asks what did kill Lynley, the Doctor responds, "Witchcraft."
Meanwhile, Lilith entrances Shakespeare and, using a marionette, compels him to write a strange concluding paragraph to Love's Labour's Won. She is discovered by the Bard's lover, whom she frightens to death. On hearing another scream, the Doctor runs in and finds the body. Through the window, Martha sees a witch fly away.
In the morning the Doctor, Martha and Shakespeare proceed to the Globe Theatre, where the Doctor asks why the theatre has 14 sides. After hearing Shakespeare's explanation, the three visit the architect, Peter Streete, in Bedlam Asylum. The Doctor helps Streete to emerge from his catatonia long enough to reveal that the witches dictated the Globe's design to him. The witches observe this through their cauldron. Doomfinger teleports to the cell and kills Peter with a touch. The Doctor identifies the witches as Carrionites, a species whose magic is based on the power of words.
Back at the Elephant, the Doctor deducesthat the Carrionites intend to use the powerful words of Love's Labours Won to break their species out of eternal imprisonment. The Doctor tells Shakespeare to stop the play whilst he and Martha go to All Hallows Street to thwart the witches, explaining to Martha that if they don't stop the Carrionites, she and the rest of the human race will fade. The Doctor and Martha reach All Hallows Street and confront Lilith, who is expecting them. She confirms the Doctor's suspicions.
Lilith steals a lockof the Doctor's hair. Taking flight through the window, she attaches the hair to a doll — which the Doctor explains is essentially a DNA replication module — and stabs it in the heart, whereupon the Doctor collapses. Assuming that he is dead, Lilith flies to the Globe. Martha helps the Doctor restart his left heart before the duo race to the Globe. Meanwhile, the actors have already spoken the last lines of the play, a series of directions and instructions that have opened a portal allowing the Carrionites back into the universe. The Doctor tells Shakespeare that only he can find the words to close the portal. Shakespeare improvises a short rhyming stanza but is stuck for a final word. Martha comes up with Expelliarmus (a word from the Harry Potter novels), which is shouted at the Carrionites. The Carrionites — together with all the extant copies of Love's Labour's Won — are suckedback through the closing portal. Martha, The Doctor finds the three witches trapped, screaming in their own crystal ball and appropriates it for safe-keeping in the TARDIS. The confused audience eventually begin clapping, believing everything to be part of the performance.
Before they depart, the two share a few parting words with the author in which he announces that he knows Martha is from the future and the doctor is alien and Martha realises that Shakespeare is taken with her when he refers to her as his "Dark Lady" Then, Queen Elizabeth arrives at the Globe, having heard of last night's performance. Upon seeing the Doctor, she immediately sends her guards after her 'sworn enemy'. The Doctor-intrigued as to how he will later upset the Queen- runs for the TARDIS with Martha.
The Doctor and Martha narrowly escape an attack by the Family of Blood who are seeking the Doctor's Time Lord life force to prevent themselves from dying out. As the Doctor directs the TARDIS to Earth, he tells Martha that he must transform into a human for three months to escape the Family's detection while they die, and gives her a list of instructions to follow. He then uses the Chameleon Arch to transfer his Time Lord configuration to a fob watch which he asks Martha to guard.
After landing on earth in 1913, a year before the Great War, the Doctor adopts the persona of John Smith, a schoolteacher at Farringham School for boys, while Martha acts his maid. John's personality is nearly opposite of the Doctor's, being quiet and timid, but faint memories of the Doctor slip through in dreams, appearing as text and images he writes in his "Journal of Impossible Things". Though John carries the fob watch, the perception filter that it possesses prevents John from being curious about it. John has become infatuated with the new school nurse, Joan Redfern, and shares his journal with her; Martha remains concerned, as the Doctor did not instruct her what to do, should he fall in love. Timothy Latimer, a younger student at the school with extrasensory perception, discovers the fob watch and pockets it for himself, unbeknownst to Martha.
Meanwhile, the Family of Blood have been able to track the Doctor to Earth, and cover their ship in an invisibility shield to keep it from being discovered. The various members of the Family seek out human victims to possess, including one of the school's prefects, one of Martha's fellow maids, a farmer, and a young girl with a balloon, allowing them to seek out the Doctor undetected. When Timothy briefly opens the watch and experiences portions of the Doctor's memories, the Family detects its presence at the school, and soon recognises Martha. They try to get information from her about the Doctor. Martha realises that the Family has found them and attempts to retrieve the watch in order to bring back the Doctor, but cannot find it. She talks to John and tries to awaken the Time Lord persona, but instead causes John to become angry with her, forcing her out of his chambers as he prepares for a village dance with Joan that night. At the dance, Martha again tries to persuade John to become the Doctor by showing him elements of his past such as his sonic screwdriver, but is unaware that the Family has overheard her conversation. Now aware that John is the Doctor, the Family captures both Martha and Joan. The cliffhanger ending leaves the Family asking John the question of "Maid or matron, your friend or your lover. Your choice."
The Family of Blood hold Martha Jones (Freema Agyeman) and Joan Redfern (Jessica Hynes) captive at the village dance and are forcing the Doctor (David Tennant), hiding as "John Smith, human", to choose one of them to sacrifice. As John struggles with the dilemma, Timothy Latimer (Thomas Sangster)—in possession of the Doctor's fob watch containing his Time Lord "essence"—opens it briefly, which momentarily distracts the Family, enabling Martha to grab Mother's gun and escape with John, Joan, and the others back to the school, where John helps to organise the school's defenses while Martha and Joan search for the watch.
The Family assault the school with an army of scarecrows, but the schoolboys defend against the first wave. When the Family shows John that they have discovered his TARDIS, Joan accepts the truth—John really is the Doctor. As the Family continues their assault, John, Joan and Martha escape to the home of the Cartwrights, family of the little girl whom the Family had taken, where they are found by Tim Latimer, with the watch.
Discovering that the Doctor has escaped, the Family begins an aerial bombardment of the village. Sheltered in the Cartwright home, Martha and Joan implore John to use the watch to become the Doctor and save everyone. John is reluctant. He loves the life he has, but Joan understands that the Doctor is needed now.
John boards the Family's ship, surrendering the watch and pleading for the bombardment to stop. When the Family open the watch, it's empty—John has already changed back into the Doctor. After a warning, the Doctor wreaks calm, merciless retribution: he gives them a hellish form of what they sought—immortality. He pushes Mother of Mine out of the TARDIS into the event horizon of a collapsing galaxy, wraps Father of Mine in unbreakable chains forged in the heart of a dwarf star, traps Sister of Mine in every mirror in existence, and suspends Son of Mine as a scarecrow. The Doctor returns to Joan, offering her a chance to join him aboard the TARDIS, but she declines. The Doctor leaves his journal with her.
Timothy bids goodbye; the Doctor gives him the now-ordinary fob watch to keep. Years later, a World War I battle rages. While helping Hutchinson, Timothy recognises the moment from an earlier vision, thus avoiding a shell strike; both survive the war. In Timothy's old age, he spots the Doctor and Martha in attendance at a remembrance ceremony. Timothy and the Doctor silently acknowledge each other.