A woman, Lilith, looks on from her balcony as a man serenades her from the street. She invites him in but the house is filled with strange, disturbing items. She kisses him and transform into a hideous witch. She then invites her 'mothers', two twisted hags, to attack him.
The Doctor is taking Martha on her first trip and it's a rocky ride. They arrive in London in 1599, and go for a stroll, heading for the newly-opened Globe Theatre. He takes Martha in to see one of Shakespeare's plays, Love's Labour's Lost. After the play, Shakespeare comes on stage to accept a round of applause from the audience. Up above, a lady looks on from a private box and strokes a doll in the image of Shakespeare. He mocks the audience but then staggers as the woman kisses the doll. He pauses and then talks of showing Love's Labour's Won the next night, raising the Doctor's suspicions since this was one of Shakespeare's 'lost' plays.
Shakespeare meets with his friends who say the new play isn't ready yet. The Doctor and Martha burst in and Shakespeare is impressed with Martha. The Doctor tries to use his psychic paper on Shakespeare but the author realises it's blank, demonstrating his enhanced mental abilities. An official, Lynley, comes in and warns Shakespeare that if the play isn't properly registered, he'll cancel it. As he leaves, he bumps into Lilith, who realises that Lynley poses a threat to the play's performance. She uses the doll to 'drown' him on dry land. The Doctor and Martha hear his screams and find the man choking up water. Lilith then pounds the doll's heart, killing the official. The Doctor sees that something is amiss.
Lilith meets with her two Mothers, Mothers Doomfinger and Bloodtide, and they discuss how to ensure that Love's Labour's Won is performed. Martha and the Doctor return to Shakespeare's rooms where he realises that there is something odd about them. The two time travellers go up to the room and end up sharing the bed, but the Doctor is distracted, considering where the psychic energy came from to kill Lynley.
Lilith returns to the tavern where Shakespeare is working, and releases a green mist that causes the author to pass out. She then uses a puppet-doll to "guide" Shakespeare in his writing. The serving girl Dolly comes in and Lilith attacks her. The woman screams; the Doctor hears and comes down to find the girl dead of fright. Martha runs to the window and sees Lilith ride away on a broomstick.
The next morning they discuss Dolly's death and Shakespeare mentions the architecture of the Globe Theatre. They investigate the theatre and the Doctor notes the unique fourteen-sided designed. The Doctor suspects the theatre is used to influence people's minds and decides to talk to the architect, Peter Streete. Shakespeare warns that Peter went insane and started ranting about witches, and they go to the asylum to speak to him. Meanwhile, actors practice Love's Labour's Won in the Globe, disturbing the ether and opening a portal where a hooded figure looks down upon them before disappearing. They resolve not to say anything about it so they don't get labelled as mad.
The Doctor goes in to see Peter, and the three witches sense him there and notice something unusual about him. The Doctor tries to get through to Peter so he can tell the story of the witches. Mother Doomfinger goes to confront the Doctor while Peter speaks of how the witches 'whispered' to him, telling him how to build the Globe Theatre to their design, then "snapped his wits." The Doctor gets him to tell where the witches were but Mother Doomfinger arrives and kills Peter before he can say anything else. The Doctor confronts her, saying he needs the right word. Realising that 14 is key, the Doctor names her as one of the Carrionites, and she disappears.
The Doctor explains that the Carrionites seek death and destruction and realises that the new play is a weapon, and they head for the theatre. As the play is performed and the witches observe, Shakespeare bursts in to end the performance. The witches use the doll to render Shakespeare unconscious, while the Doctor and Martha go to the witches house. The house of Lilith's door swings open and they enter, where Lilith greets them. Martha tries to "name" her but nothing happens - Lilith states that the power of a name works only once. She names Martha, only rendering her unconscious since she's "out of her time". Lilith cannot name the Doctor, and tries to use the word 'Rose', but this only inspires him. Lilith states that the Carrionites were banished by the Eternals, but they found new words from Shakespeare after the death of his son and gained a new power to travel to Earth. Then after the play is performed, the rest of the Carrionites will appear and purge the Earth. She snips a piece of his hair then levitates out the window and attaches his hair to a puppet. She hits the doll's heart, causing the Doctor to collapse, but Martha awakes. and realises that since he has two hearts he is okay. Martha gets his second heart working and they race to the theatre.
Lilith meets with the other witches at the Globe Theatre, and the final lines are recited, opening the portal for the Carrionites. Energy surges around the building as the Doctor and Martha arrive and revive Shakespeare. They go out on stage to confront the Carrionite witches as the others of their race swirl out of their globe and fill the theatre. The Doctor convinces Shakespeare to improvise and invent new words to confuse and then destroy the Carrionite invaders, the passage of their wind taking Shakespeare's "lost" script with them. The astonished audience applauds while the Doctor goes up to find the power sphere, in which the three witches are trapped by Shakespeare's words.
The next morning, Shakespeare flirts with Martha but Martha remains uninterested. The Doctor suggests Shakespeare not try to rewrite Lost Labour's Won. the Doctor prepares to take the witches' globe into the TARDIS, and Shakespeare reveals that he knows they are time travellers. Shakespeare gives Martha one final sonnet and then Queen Elizabeth I arrives to ask them to perform. She recognises the Doctor as her "sworn enemy" and tells his guards to kill him. The Doctor and Martha are forced to run for the TARDIS and make a hasty escape.