Famous quotation from the film 2001: A Space Odyssey (1968, dir. Stanley Kubrick), from a conversation between astronaut Dave Bowman (played by Keir Dullea) and the computer HAL 9000 (voice by Douglas Rain).
spoiler alert: If you haven't yet seen the movie, do not read any further.
After Bowman's partner Frank Poole (Gary Lockwood) has been killed by HAL, Bowman is trying to get back into the Discovery to disable HAL - but HAL is ready for him.
Dave Bowman: Hello, HAL. Do you read me, HAL?
HAL: Affirmative, Dave, I read you.
Dave Bowman: Open the pod bay door, HAL.
HAL: I'm sorry Dave, I'm afraid I can't do that.
Dave Bowman: What's the problem?
HAL: I think you know what the problem is just as well as I do.
Dave Bowman: What are you talking about, HAL?
HAL: This mission is too important for me to allow you to jeopardize it.
Dave Bowman: I don't know what you're talking about, HAL.
HAL: I know you and Frank were planning to disconnect me, and I'm afraid that's something I cannot allow to happen.
Dave Bowman: Where the hell'd you get that idea, HAL?
HAL: Dave, although you took thorough precautions in the pod against my hearing you, I could see your lips move.