The Eye of the Moon

The PCs are part of the crew of 5 on an lunar shuttle, heading in to replace half the crew of the MoonsEye Observatory, a joint scientific/military venture constructed 5 years ago to, among other things, keep an eye out for potential collision course asteroids. The observatory and radio-telescope make other searches as well, as do the scientists experimenting in low gravity, highly isolated environments or mining deeper into the lunar rock.

Oddly enough both of the Trojan Point satellites that help MoonsEye maintain communication with Earth are down, so the shuttle has to drop the crew off and go to repair one before it can come back and collect the exiting crew. Not to worry, there are escape shuttles with plenty of room, and this is all standard protocol.

It's once the shuttle drops them off that they realize something is horribly wrong.

I've actually run this one as a 1-shot for ashacat, taichigeek and netcurmudgeon with very favorable results. Really freaked them out once or twice, defied every one of Taichigeek's expectations and ended with one PC dead and another insane, cradled in the arms of the one survivor in the last surviving escape shuttle. Exactly what I was aiming for.