I'm not going to pretend like the Knight Watchman "really" dies: he doesn't, it's a trick of some sort. This isn't a spoiler, it's common sense. Besides, why would anything be as it seems when you're dealing with the equivalent of Bat-Mite, Knight-Sprite?
Blah blah -- it's the work of Knight-Sprite, a cartoonish jester with near-limitless power, who likes to mess around with the Dauntless Duo.
Knight-Sprite sends Galahad back to the regular world, and Galahad somberly realizes that the Dimension X thing was all real after noticing scratches on his arm from the snake attack. He swears to live up to the Knight Watchman's legacy as a solo 11-13 year old hero.
Almost immediately he sees a crime in progress, with crooks he recognizes hiding out in a warehouse. He busts in to take them out, but since he's outnumbered 4-to-1 and half their size, it doesn't go so well for him. That's when dun dun duuuuun the Knight Watchman arrives on the scene.
Oh, and when they get home, there's a surprise birthday party for Jerry, because I guess it was his birthday all along and nobody mentioned that. Reid converted their basement into a basketball court as a gift, which seems a little ostentatious but I guess he's sort of rich.
Moving on, we've got the stunning origin of Gorilla Cop! That's right, Big Bang even has its own version of Detective freakin' Chimp. While Detective Chimp was a regular chimp granted intelligence by the fountain of youth or something, Gorilla Cop was a regular cop turned into a gorilla by an "evo-ray".
Sam Douglas is a regular beat cop; he's best pals with his old partner Artie and has a swell girlfriend named Kim, whom Artie is secretly hot for. Sam investigates a light in an abandoned warehouse and is captured by Dr. LA Mental, whose "evo-ray" needs to absorb evolutionary energy by devolving people into gorillas in order to evolve someone further.
Sam is turned into a gorilla by the ray, and is about to be put in a drug-induced rage like Mental's other victims when Artie bursts in. Mental flees, leaving Sam in possession of his faculties (apparently the evo-ray doesn't devolve brains, even though Mental's plan hinges on it evolving his own). Sam can't speak, but tries to tell Artie who he is by flashing his gold tooth, which the evo-ray naturally shaped into a simian canine what do you want from me
That's not quite as silly as it sounds -- after all, Artie saw Sam go into the warehouse and never come out.
This story moves along at a blistering pace from here on out -- Sam (who I'm just gonna call Gorilla Cop from now on) sneaks back into the lab that night to see if he can figure out how to change back or something like that. He discovers an unconscious Artie, Mental, and his girlfriend Kim in a cage. It's not really clear why Mental captured Kim -- I guess he figured Gorilla Cop would come back and wanted leverage. He's used the ray to evolve into the super-intelligent, psychic space guy seen above, but Gorilla Cop deftly smashes the ray gun, causing it to backfire on Mental and devolve him into nothing (while dooming himself to life as a gorilla; compare Hummingbird's origin) Oh, and he can talk now, because he tried really hard.
As is often the case with a Silver Age pastiche (and many real Silver Age stories), I sort of have a lot of questions -- Gorilla Cop clearly got promoted, so he's not on the beat anymore, but he's not a detective, so is he the guy behind the desk at booking or the evidence room or something now? Hell, what does this mean for his relationship with Kim, or Artie's relationship with Kim? And I'm almost positive there isn't a second Gorilla Cop story to clear any of that up, too. Wait, am I really clamoring for more of this? Big Bang Comics, the things you do to me...