An alien parasite with the ability to possess human bodies goes on a violent crime spree in LA, pursued by a human cop and an alien cop inhabiting a human body.

Doctor: Detective Beck. No one deserves to die like that. I don't care what the man's done.
Cliff Willis: He killed twelve people, wounded twenty three more, stole six cars, most of them Ferraris. Robbed eight banks, six supermarkets, four jewelery stores and a candy shop. Six of the ones he killed he carved up with a butcher knife. Two of them were kids. He did all that in two weeks. If anyone deserves to go that way, it sure in the hell was him.
Tom Beck: You know what bothers me about these two guys DeVries and Miller?
Lloyd Gallagher: Neither has a criminal record. They both lead normal lives until a few days ago, and now they're killing people.
Tom Beck: Do you read minds or was that just a shot in the dark?
Lloyd Gallagher: No, I read minds.
Tom Beck: Oh yeah? What was I just thinking?
Lloyd Gallagher: That I'm full of shit.
Tom Beck: Impressive.
Lloyd Gallagher: Not really. Quite simple to read.
Lt. John Masterson: Look, Ed, Tom Beck is the best I've got. If I give him to you, I'll never get him back again. My department will then crumble, crime will run rampant, the city will fall into ruin, rampaging hordes will control the streets, and life as we know it will end.
Tom Beck: Doesn't anyone say please any more?
Lloyd Gallagher: Please.
Tom Beck: How can I refuse?
Lloyd Gallagher: You can't.
[Lloyd takes Beck for a ride in his Porsche]
Tom Beck: Bureau must be paying pretty good these days.
Lloyd Gallagher: Pretty good.
Tom Beck: Mind me asking how much one of these costs?
Lloyd Gallagher: No.
Tom Beck: How much?
Lloyd Gallagher: I don't know.
Tom Beck: You don't know? What did you do, steal it?
Lloyd Gallagher: Yeah.
Tom Beck: Oh, thank you. That is illuminating. That solves everything. Christ, Miller doesn't have a chance. Hey, why would he come in here and kill a guy for a lousy hundred bucks and a radio?
Lloyd Gallagher: Because he likes it. He sees something he wants, he steals it. If something gets in his way, he kills it. And right now, he's hiding out in your city.
Tom Beck: What the hell is that?
Sanchez: A flame-thrower man, can you believe it? Patrol picked this up off some homeboy on the street.
Tom Beck: I'll cover you.
Lloyd Gallagher: I'd be safer if you didn't.
Tom Beck: Fine, I won't cover you.
Lloyd Gallagher: Alright, cover me.
Tom Beck: Do you want me to fucking cover you or not?
Lloyd Gallagher: I need you to cover me.
Tom Beck: Fine. I'll cover you.
Prisoner: Yo, hippy, what kind of dude are you?
Lt. John Masterson: Alhague!
Lloyd Gallagher: Yes?
Lt. John Masterson: Before I kill you, I'm curious: how did you find me?
Lloyd Gallagher: You left an angry partner for dead on Altair.
Lt. John Masterson: A mistake.
Lloyd Gallagher: That's what it said.
Tom Beck: I want to ask you if I'm crazy, or does this seem just a little bizarre?
Lloyd Gallagher: Yeah, it's a little bizarre.
Tom Beck: I knew that. I just wanted to know if you knew that.
Barbara Beck: Where did you grow up?
[Lloyd points upwards]
Barbara Beck: What is that? North?
Lt. John Masterson: Alhague, how do you like being human?
Unknown prisoner: [distant] Say, what?
[At this revelation, Tom Beck looks at Lloyd. Lloyd looks back]
Lloyd Gallagher: It's all right.
Lt. John Masterson: Better than being Altairian. Altairians are a filthy people. We could take over this place if we wanted. They have nothing here to stop us.