This is a novelization of the tenth-anniversary celebratory episode of Doctor Who, which was the first serial of the tenth season and was broadcast December, 1972-January, 1973. All three versions of the title character from the first decade of the show appear, though the only official companion was Jo Grant, the feisty UNIT member who traveled with the third iteration. UNIT operatives Brigadier Lethbridge-Stewart and Sergeant Benton also figure in the story; in fact, Dicks gives many of the best lines to Benton. His adaptation is, of course, based on the teleplay, which was written by Robert Baker and Dave Martin. It also seemed to me that the second version of The Doctor kind of upstaged the current star in the book. The original Doctor is trapped and interacts only electronically. It's a fun, if simple, story, about a foe so ominous that Time Lord law has to be bent and broken in order to face it down, thus allowing the triple-convergence. The mad Time Lord Omega threatens all of existence from his anti-matter prison, but the real thrust of Dicks' book is the amusing interplay between the characters. The ending is fun, too, with everyone going back to when they belong, and the current Doctor rewarded with a part he needs to repair his TARDIS. This was the first multi-Doctor story, and the success led to many of the most popular future adventures.