In his closest approach yet to self-parody, Bellairs sends an assortment of characters back in time for a series of surreal, hair-raising adventures. Behind a bricked-up door in his old house, Professor Childermass discovers a trolley that's been modified to travel in time. He concocts a harebrained scheme to go back 500 years and save Constantinople from the Turks; his two young friends, Johnny Dixon and Byron ("Fergie") Ferguson, find him out and invite themselves along. Amidst a confusion of Turkish, Greek, and Venetian soldiers, the three meet Aurelian Townsend--the trolley's modifier--and are variously chased, captured, wounded, and miraculously healed, saved by ghosts, and forced to take a pop quiz by a menacing magic Guardian ("Name the seven kings of Rome"); they also wend their way through tunnels and fly through the air. In the climactic scene, they temporarily save a crowd massed in Hagia Sofia when the professor's snide familiar, the Egyptian god Horus (also known as Bradley), frightens the Turks away with the apparition of a huge falcon singing "The Bear Went Over the Mountain." The companions finally return to the trolley and--after a brief side-trip to a spooky future--lurch safely back to their own time. Brace yourself for a wild, herky-jerky, tongue-in-cheek ride, not as gruesome as Eyes of the Killer Robot, but full of danger nonetheless.