DOCTOR: People who talk about infallibility are usually on very shaky ground.

(The telephone rings.)

BENTON: Sergeant, Acting Governor Benton here.

BRIGADIER: This is Brigadier Lethbridge Stewart of UNIT. This prison is now in military hands.

(A sniper shoots the megaphone out of his hand, so the Brigadier kills the man with a fast draw of his revolver.)

JO: Never mind, Doctor. You’ve beaten him.

DOCTOR: Have I, Jo? He’s got his TARDIS back. He’s free to come and go where he pleases, while I’m stuck here on Earth (pause) with you, Brigadier!

(Brigadier smiles.)

JO: Doctor, what did you see?

DOCTOR: Fire.

JO: But why should you?

DOCTOR: Well, some time ago, Jo, I witnessed a terrible catastrophe. A whole world just, just disappeared in flames. Well, this machine picked that memory out of my mind and used it to attack me.

JO: This fire you saw, it wasn't real.

DOCTOR: Neither was the water, nor the rats, yet Linwood is dead and so is Professor Kettering. We believe what our minds tell us to, Jo.