With The Time Trap, first of the two titles in this fourth volume, Jacobs tackles a quintessential science-fiction trope: time travel. Dinosaurs, medieval knights, and an apocalyptic future make it a fabulous adventure, and who cares if, for the first time, Olrik isn't there?

The Affair of the Necklace, on the other hand, is a pure crime story done in ultrarealistic overtones that set it somewhat apart from the rest of the series. Finally, the extra material will shine a light on the dangers of censorship at the time - from which even Jacobs wasn't safe.