The Doctor and Graham were arriving at what was supposed to be Aruba. Instead, what they find is the barrel of a gun in an empty alley. They are then shot immediately.
Cue title sequence and episode title: Thirteen Minutes
Graham is having trouble breathing. Getting shot in the lungs will do that to you. The Doctor tries to call for help, but all she does is cough up blood. She finally realizes something: one of her hearts has stopped.
She tries to get up, but just falls back down. Graham's breathing is slowing down, so Doctor decides to try and keep Graham entertained. She finally tells him the story of who she is, and why she calls herself the Doctor. By the end of her story, she finally noticed that Graham stopped breathing. He was dead.
She cries to herself for a bit, partly from the pain in her working heart and the loss of her friend. She calls for help, but no one comes. She is completely alone. She accepts her fate as she sings to herself, looking to the stars, until, after thirteen minutes, she is finally wounded enough to trigger her regeneration.
She goes from a woman in her thirties, to a boy in his teens. Unruly hair, not unlike his thirteenth body but jet black instead of silver, and tanned skin. He looks around his surroundings, and when he gets to Graham, he gets to his feet and goes to him, knowing it's too late to save him.
He silently sets his body outside the alley to be found before walking back into the TARDIS. All the pent up anger is finally released onto the console, causing the whole room to catch in flames. He allows himself to be swallowed by the flames, hoping to find salvation within the flames, but all it does is allow excess regeneration energy to heal the burns. With the flames dying down and the console room being refurbished into a an empty room with the stars as the ceiling, the Fourteenth Doctor breaks down and cries.
Roll Credits: The Doctor Will Return in - Cold Open