Will accidentally catches Chronos, the titular merchant (John Crawford), while trying to slow cosmic particles. Angered by the waste of his time (the commodity in which he deals), the cranky chrono-peddler demands that Will give up some of his allotted time in recompense, only to become even angrier when he discovers than Smith has made free use his time machine to return to Earth just before the launch of the Jupitar 2. Well-structured, logical time-travel stories are extremely difficult to write, so don't expect this simplistic plot to make a lot of sense (it is unclear if there are temporarily two robots, two Smiths and two Wills in 1998 or why when you go back in time your clothes change accordingly (if your Smith but not if you're Will)). Smith shows more humanity than usual when he discovers that, unless he resigns himself to returning to 'lost in space' status, the resulting alteration of the Jupitar 2's time-line will kill the Robinson family. Chronos, who varies between being some kind of grasping 'dealer in time' to being an all-powerful equivalent of the Greek fate Atropos, is the show's usual eccentric, blustering scoundrel but his time-manipulation equipment is colourful and the Daliesque touches are witty. Entertaining and an improvement over other season 3 episodes but best enjoyed by the right side of the brain only.