Molly and Her Other Self 1976.

The quack followed you with his eyes the moment you entered his room accompanied by two burly nurses, and didn't relax until you were sitting in the chair opposite him with the two nurses nurses not far away. The last mind quack you attacked and almost strangled with his tie and tried to poke out his eyes. You studied him, your eyes searching his eyes, watching his facial muscles, studying his hands. He began asking you, as they all did, how you were and if the medication was helping, which you ignored, letting one of the nurses give her assessment of how you were. See, your other self said inside your head, he's afraid, you can see it in his eyes, in the movement of his muscles; you could have him if you wanted to; the two nurses are unaware, after a while, that you might attack. You ignored her, let her voice in your head rattle away as it often did. He smiled nervously when you smiled, eyeing the nurses, playing with his fountain pen between fingers. You said little in replies. but still he went on giving his judgement of your case, why you had murdered your boyfriend and his two friend and his sister, his mouth moved, the words coming out. But you were watching his pen, how he held it loosely between fingers, his mind elsewhere, the nurses behind becoming bored. Go, the other self said, and you leapt up and grabbed the pen and jabbed it into his open hand, jabbed it in deep, and didn't stop until the nurses jumped you from behind, and took you to the ground, and his cursing and wearing the only other sound.