Because I’ve said it before, and I’ll say it again - Brad Dourif was the best damn guest star this show ever got its hands on. Half the supernatural element here is how damn fantastic he is. That’s just not normal. And I’ll say it: I found Boggs so compelling, a little part of me was sad that they killed him (even if he did deserve it).
The whole thing is just freakin’ creepy. Scully’s all alone, and then along come the terrifying cult folks, and they catch her and they happily beat the crippled guy to death with a rock and remove a big damn parasitic slug from him so that they can transfer it into Scully. And she’s screaming at them and they’re coming for her and it’s that moment when normally, you’d expect some Eleventh-Hour rescue, Scully would get free somehow…but she doesn’t. She gets slugged. Damn.