The Edge of Destruction
Something shakes the TARDIS violently. All four passengers fall to the ground and pass out. Barbara is the the first one of wake up. Eventually the other wake up. Susan acts very strange. The doors to the TARDIS are open but when Ian starts to approach them they close on their own. Susan says that's impossible.
The Doctor has suffered a head wound. Susan gets a bandage for it. Barbara applies the bandage to the Doctor's head. Susan goes to lie down. Ian goes to see her. She has a knife and threatens him with it and continues to act very odd.
Barbara and the Doctor gets into an argument over nothing at all. Ian, Barbara and Susan all go to sleep. The Doctor doesn't know where the TARDIS is. The episode ends with the Doctor by the console. Someone grabs him from off screen by the neck.