The Pyramid is baacckk! Well, actually, it never went away - but it had seemed to be inactive, still sitting in the middle of Chicago but no longer growing and wiping out buildings as it grew.
The pyramidal device sent by the Krin to dominate the Earth had suffered a severe setback when the motley crew of ivory-tower academics, paratroopers, and one resourceful maintenance man had not only survived the worst that both the gods and mortals of Classical Greece and ancient Egypt could do, but had managed to escape from the ur-mythological world that the Krin pyramid had somehow brought to deadly life in a parallel dimension, bringing several beings out of myth along with them.
The Krin device would have been thwarted, if things had been left as they were - but a V.I.P., who knows too many state secrets to be allowed to be missing, was left behind in the world of Greek mythology. So a power-mad Washington bureaucrat has press-ganged several of the survivors of the first excursion into the pyramid's worlds and sent them, along with a team trained in "surgical strikes," to either bring back the V.I.P. or, if that's impossible, terminate him with extreme prejudice.
Unfortunately, instead of returning to mythological Greece, they find themselves in the world of the Norse gods. Even if they manage to survive the enmity of Odin and his warriors, can manage to free Loki (a potential ally) and can keep the hard-drinking thunder-god Thor off the sauce long enough to help them, Ragnarok is coming, with the end of the world. And even a hard-headed maintenance man may have trouble fixing that problem!