Point of No Return: I always enjoy these stories with the UFO nerds being really onto something. Also pleased this one didn't die, as I recall there was an X-Files with some decent UFO nerds who died, or maybe that was in Sanctuary. Noooo don't kill the nerds!!
That episode spawned an interesting spin-off pilot on the WB which sadly didn't get picked up, which is frustrating because they'll air all sorts of cr*p.