Schisms, TNG 6
Several members of the crew discover that they are being abducted by… ALIENS! Aliens in space? Next we’ll be afraid of g-g-g-ghOOOOsts!
They aren’t just any aliens, though, they are from the 18th dimension (or so) and they have created a pocket universe of our space in a supply closet of a cargo bay (or something) and are doing experiments. Some alarmingly bad effects and truly baffling techno-babble make this episode sub-par.