SCULLY: Well, my best guess would be that he's been exposed to some kind of chemical refrigerant, like liquid nitrogen, possibly even ingested it.

MULDER: Well, you see what happens when you drink and drive?

SCULLY: How many people can do that?

MULDER: Just about anybody who's up for that grant money could.

LISA: It's a kind of catalyst.

SCULLY: A catalyst for what?

LISA: A self-sustaining endothermic reaction. It's a rapid freezing agent - something Jason's been engineering for years. See, when a cell freezes, its moisture forms into ice crystals, which literally grind up the cell from the inside out. But extreme rapid freezing causes a smoother, glass-like structure to form instead. So the cell can survive being thawed.

SCULLY: This isn't gonna work.

MULDER: Why not?

SCULLY: His body temperature was 8 degrees. The lowest reported body temperature ever survived by a human being was 70.

MULDER: Well, if he's already dead, then he's got nothing to lose.

SCULLY: It's a celebration, but of what?

MULDER: Or something that never happened.

SCULLY: What? Mulder, this is a photograph. It is a documented moment in time.

MULDER: In a future that somebody is trying like hell to prevent from happening.

SCULLY: What?

MULDER: Think about it, Scully. If Lucas Menand never gets hit by the bus, his complaint gets heard before the grant committee. Jason Nichols loses his funding and he never gets to collaborate on his research with Dr. Yonechi. Therefore, this photograph never gets taken because this celebration never happens.

SCULLY: And if your sister is your aunt and your mother marries your uncle, you'd be your own grandpa.

SCULLY: OK, so this photo that was never taken, when was it never taken.

MULDER: At least five years in the future, when they first synthesized the freezing compound successfully.

SCULLY: Mulder, the compound already exists. We have physical evidence.

MULDER: Only because the old man brought it back with him.

SCULLY: Back from where?

MULDER: From when may be the real question.

SCULLY: You're seriously suggesting that this old man is back from the future? So what you're saying here is the old man is ...

MULDER: Jason Nichols. Although common sense may rule out the possibility of time travel, the laws of quantum physics certainly do not. In case you forgot, that's from your graduate thesis. You were a lot more open-minded when you were a youngster.

SCULLY: I know what I wrote, Mulder. I also know that the laws of physics would permit the theoretical possibility of time travel, but the limits of human endurance would prevent such a trip from ever happening.

OLD MAN: Thirty years ago - ten years from now - you'll be at a conference in Zurich. You'll meet a man named McGuane who's just discovered the first evidence of tachyons - subatomic particles that can travel faster than the speed of light and go back in time - but only for a few seconds and only at a temperature of absolute zero.

MULDER: The man we're looking for - the old man - he's you. If that photo is indicative of a pattern, you may be his next target. It puts a whole new spin on being your own worst enemy, huh?

MULDER: Physicists like Stephen Hawking have hypothesized the existence of wormholes and closed time loops, actual portals through which matter can travel backward through time. Although, phenomena like extreme heat and gravity would render the trip lethal for any organism.

JASON: So you're saying the properties of my compound will make it possible?

MULDER: Eventually, yes, that's what I'm saying.

JASON: But why stop time travel?

MULDER: I know what I saw, Scully, and I know what I believe happened.

SCULLY: Even if it can never be proven?

MULDER: Never? Never is a very long time, Scully, you said that yourself. "Although multidimensionality suggests infinite outcomes in an infinite number of universes, each universe can produce only one outcome."

SCULLY: I was 23 when I wrote that.

MULDER: Yeah, but I take that to mean that you were suggesting that the future can't be altered. Which means that the elder Jason Nichols' attempts to stop his own research will fail, and that eventually his compound, and time travel, will be discovered.