They try to stop him from opening the casket, but there's no way in hell he's going to do that. Mulder cracks it and catches sight of a spindly body within. Not in the shape you'd expect from an embalmed corpse - and even if it were, it wouldn't be human, anyway. That's not a twenty-year-old boy, no matter how you slice it.

He looks up, catching Scully's eyes, and for a moment, he's almost gleeful. Look what we found - and it really is a 'we.' He'd half-expected her to stay uphill, looking down disdainfully. Instead, she kept up with him.

And then he's all business, barking orders. "Seal this up! I want this casket moved immediately. No one looks at it, no one touches it."