Battlestar Galactica, Season 4

[Tigh comes to Adama's quarters just before the extremely risky attempt to rescue the Baseship hostages begins]

Colonel Saul Tigh:
Bill, you gotta scrub this mission.

Admiral William Adama:
What the hell are you doing here? You're supposed to be in the CIC.

Tigh:
The Cylons will kill every godsdamn hostage before we put one pair of boots aboard their ship. Laura Roslin will be the next to die, Bill.

Adama:
I'm looking for options. You got one?

Tigh:
Yeah. I should've told you when I first found out, but I didn't have the guts.

Adama:
What's wrong with you, Saul?

Tigh:
You remember back at the nebula when I told you about that frakking music? I thought it was in the ship. I was wrong. It was a signal. Some kind of crazy, frakked-up Cylon signal switched me on. I can't turn it off.

Adama:
[not wanting to understand] Switched you on.

Tigh:
Like Boomer. I'm one of the Five.

Adama:
The Five.

Tigh:
One of the Cylons D'Anna's after.

Adama:
[rising from his desk] Quit frakking with me. Colonel, I've known you for 30 years. When I met you, you had hair. I've never heard of a Cylon aging.

Tigh:
Doesn't mean they don't. Before the attack on the Colonies, we didn't know the skinjobs existed. Turns out there's another kind of Cylon we didn't know about, and I'm one of them.

Adama:
[desperate] On New Caprica, you were in captivity. They did something to you, they... An implant, a post-hypnotic suggestion that makes you feel this way. Let's go talk to Doc Cottle...

Tigh:
[grabs Adama by the shoulders] Listen to me! It is not a delusion. It is not a chip in my head. I am a Cylon. I've fooled you for months now. I didn't want to, but I did.

Adama:
Get your hands off of me.

Tigh:
[releasing him] If I'd had the guts to airlock myself when I first found out, we wouldn't be in this mess. But that's the way out. Not this suicidal attack. I am one of the Final Five. D'Anna will back down if you threaten to flush me out an airlock.