This time, it's not the TARDIS that dematerialises in the wrong place for a change, but a star cruiser that comes out of warp and crashes headlong into a scientific venture aboard the ominously named "Hecate". Their distress beacon is what brings our travellers to the rescue, and quickly they are embroiled in some intra-temporal shenanigans that release the "Mandrels" from another dimension onto the ship who begin eating the economy passengers! It's also a bit worrying that there is a drugs smuggling operation going on here too - and, of course, the "Doctor" (Tom Baker) and "Romana" (Lalla Ward...