On a wartorn planet, a soldlier calls his young daughter, Splice, and tells her to brush her teeth, promising he'll be home soon. He's wearing a blindfold and traveling with another soldier, who is guiding him.

The soldiers discuss the fog. Maybe the enemy is made of fog. They have to keep going. There's no choice. There is an ambulance machine ahead they need to avoid.

Carson, the guide, falls down an embankment of some sort and then steps on a landmine and is killed.

The ambulance is activated. It finds the surviving soldier but says he must be destroyed because his eyes will not function for another four weeks.

He screams. The Doctor hears from the TARDIS.

The Doctor runs out to find the person in trouble. Ruby needs a second. She finally gets to the TARDIS door and calls for the Doctor, who is out of sight.

The Doctor steps on a landmine...

Ruby hears the Doctor singing. She goes to investigate. He tells her to come over carefully and watch her feet. He explains he's stuck on a landmine and he needs her to describe it. He also needs her to find a heavy object to counterbalance the landmine so he can get off it safely. He is standing on one foot to prevent the landmine going off.

Ruby explores and sees the ambulance. She finds Vader's urn, which she thinks is gross but it'll do. She comes down and the Doctor says this isn't an urn, it's a body. He tells her to toss it and catch it and estimates the exact weight as perfect for his needs. He wants Ruby to toss it to him but she refuses, instead going over to hand it to him even though that makes him nervous and could set off the landmine if his blood pressure goes up.

Ruby suggests they sing the song and she hand off the urn on the word "Skye." They do.

THe Doctor is able to put his foot down though he can't lift the other off the mine. He reads the name on the urn aloud and a hologram of Vader appears and says he is dead and needs his remains returned to his family. The Doctor questions him and learns he was killed because his blindness was a liability.

Splice shows up at the top of the hill and asks if her Daddy is there. She heard his voice.

The DOctor and Ruby try to avoid her question for as long as possible. Splice wants her Daddy. The hologram hears her voice and starts talking to her. She runs toward it but Ruby is afraid she'll step on the mine and grabs her. Splice struggles and the hologram goes away.

THe Doctor says he's okay, just got to control the adrenaline rush. He starts glowing. He says that he is the explosion.

Mundy shows up with a gun and says that the Doctor has to give back the urn as it is sacred. She is an Anglican Marine. The Doctor tells her that he is not human and if the mine blows up he will take half the planet with him.

Mundy shoots at him before scanning him and that activates the Ambulance. Ruby gets an idea and grabs the gun, going elsewhere and shooting into the air to distract the Ambulance from the Doctor.

Mundy tells RUby to shoot her. An injury is needed. Ruby is about to but Canto shows up and shoots Ruby, thinking he's rescuing Mundy.

Ruby falls down toward the Doctor and is unconscious. The Ambulance scans her and identifies her as Ruby Sunday, 3082 calendar years old (!) It can't find her next of kin.

Ruby's eyes close and the Ambulance estimates she will die in 432 seconds. It refuses to save her because she is not Anglican.

The Doctor gets angry. He needs Ruby. He tells her to hang in there. He can't think without talking to her. HE tells Mundy to surrender. The war is imaginary. THere is no one here but an algorithm. He gets an idea and tells the hologram of Vader to go into the Ambulance and change the algorithm. That's against its protocols but he convinces it.

Canto and Mundy admit their love for each other but Canto is suddenly killed. He becomes a hologram and his final message is that he loves Mundy and it's okay that she doesn't love him.

The Doctor realizes the algorithm killed Canto and is fighting back against being reprogrammed. A bunch of Ambulances surround him, chanting "Thoughts and prayers."

It seems like all is lost. The algorithm says that the Vader hologram is a virus and has been destroyed. The Doctor's landmine is about to explode. He tells everyone to run but Splice won't go without her daddy and Mundy won't go without Splice.

At the last second, Vaer takes over the alogirthm. The landmine turns itself off and the Ambulances all say "kiss kiss." An Ambulance decides to revive Ruby who wakes up and wonders what's going on.

The Doctor is thrilled that the power of parenting has ended the war.

The Doctor and Ruby watch the dawn with Splice and Mundy but the Doctor insists on leaving. He and Mundy hug and the Doctor tells Splice he's sorry her dad is gone. She says he's dead but not gone. Mundy is surprised the Doctor encourages Splice's faith when he doesn't like faith. He says he needs it anyway.

The Doctor and Ruby go off in the TARDIS. The Doctor says everyone dies eventually and what we leave behind is love.