Rigsy's Call for Help

The Doctor and Clara have just arrived back in the TARDIS, after an adventure, when the TARDIS' phone starts to ring. Clara answers it to find that it is Rigsy (who they last met in "Flatline"), asking for their help. Intrigued they arrive at Rigsy's flat in London, finding he has settled down with a wife and newborn daughter. He explains that he has no memory of the previous day and so has no idea on how he got a tattoo that is on the back of his neck. More worryingly the tattoo is counting down to zero.

Looking at his mobile phone they discover it's screen is cracked and Clara is not able to find any evidence of any activity as all the data from the previous day has been wiped. The Doctor scans Rigsy with the TARDIS, discovering that he has had contact with aliens in the last day, and is due to die when the countdown reaches zero. The Doctor feels there's nothing he can do, Clara insists that he at least try.

The Doctor and Clara attempt to help Rigsy by trying to piece together his movements over the last twenty-four hours. Assuming the presence of aliens hiding in London and after Clara mentions something called a 'Trap Street' - a street invented by map makers to catch people who would copy their maps without giving the proper credit - the three of them look for such a hidden street where aliens might be hiding. They eventually come across a Trap Street, aided by a flood of memories that Rigsy recalls once the TARDIS is able to restore the data on his mobile. Within the Trap Street they find that it is occupied by various aliens species using a misdirection system to both hide the street and to make themselves appear human to each other. They also discover Ashildr, who is acting as mayor among the group.

Clara Receiving the Call

Ashildr, still going by the name Me (see "The Woman Who Lived"), explains that the aliens are refugees, and that Rigsy had been sentenced to death for killing Anah, a two-face Janus female. He was injected with Retcon to forget what happened, and then given the time to say goodbye to his family. She also reveals that the tattoo is a Chronolock that leads a Quantum Shade, which appears normally as a raven, to its bearer anywhere they might flee to - killing the victim at the predetermined time when the countdown reaches zero. The Doctor and Clara though believe that Rigsy did not kill Anah and has been framed for the murder. Ashildr allows them to investigate the case, but tells them they have to convince those that live on the street of Rigsy's innocence to keep the tense truce between the various alien species that live there.

When a resident of the Trap Street is killed by the raven, for stealing medical rations, Clara learns that the Chronolock can be removed either by the person that placed it, or transferred willingly to another. Believing she is protected by Ashildr's assurance of her personal safety, Clara persuades Rigsy to pass on the Chronolock to her. So, without anyone else's knowledge, she now has the tattoo counting down on her.

Saving Rigsy

Meanwhile, during his investigation The Doctor discovers that Rigsy had called for The Doctor when he was found in the street the previous day, and believes that Ashildr was trying to contact him and lead him to the Trap Street. They speak to Anahson, the daughter of Anah who is forced to dress as a male to hide her ability to see the past and future, and confirms that Ashildr had to fabricate the mystery to bring The Doctor to her. They go back to where Anah's body is being kept, for return to Janus, but find it is a stasis chamber with a keyhole to deactivate it within a recess on a control panel.

The Doctor thinks that the TARDIS key will unlock it, and proceeds to use the TARDIS key on the keyhole but the panel traps his arm temporarily to place a metal band on his arm and to take his TARDIS key while Anah is released, alive and well. Ashildr arrives, and explains that the band is a teleportation device, a means to send The Doctor away to keep the peace on the street, and asks him for his confession dial before she activates it.

However, when Ashildr goes to remove the Chronolock from Rigsy, Clara's transfer is discovered and Ashildr regretfully reveals that she had arranged the first Chronolock with the Quantum Shade, assuring it of a soul which only she could break with no intent of anyone dying. However, by accepting Rigsy's Chronolock Clara broke the terms of that contract and now Clara is doomed to die as there is nothing that can be done to save Clara from having to face the raven that will kill her.

Discovering the Trap Street

Though Ashildr appears to be genuinely stunned and horrified at this, protesting that she never meant to harm anyone, The Doctor is furious and angrily begins to verbally attack Ashildr, demanding that she save Clara. Horrified by The Doctor's anger Clara tries to calm him down begging him not to be angry. She spends her last moments with The Doctor. She makes him promise that he will not harm anyone who will come in his way of this and will not take revenge on what has happened, reminding him why he became The Doctor. As The Doctor starts to speak, Clara silences him with a hug, telling him that everything he is about to say she already knows. Clara touches The Doctor's face in sadness, who in turn tenderly kisses her hand.

When the Chronolock counts down to zero, Clara goes outside to face the raven. The Doctor follows and watches her from afar. Refusing to run Clara stands in the middle of the street waiting for the raven accepting of her decision, as Danny Pink had done. When the raven strikes Clara screams in pain. Then the black mist of the Quantum Shade comes out of her mouth, and she drops to the ground.

After witnessing her death The Doctor returns to the others, warning Ashildr that what Clara had said was not to save him but was more directed to Ashildr and was intended to protect her. He warns her that he will do what he can to follow Clara's wishes, but advises her to stay out of his way, saying that the universe can be a small place when he is angered. Ashildr then activates the teleportation band, sending The Doctor off to an unknown location.

In a post-credits scene, Rigsy is seen putting the finishing touches on his latest bit of graffiti - a flowery mural dedicated to Clara on the front of the now empty TARDIS. He then walks away, leaving the abandoned TARDIS with no Clara and no Doctor.