Sinister Substitute

Dave's most despised teacher, a gleeful frog dissector named Ms. Veronica Krockle, is absent. Her students are psyched! But Sticky is suspicious. Especially when the substitute teacher turns out to be strangely interested in geckos. Or rather, boys with "pet "geckos.
That's no substitute! That's Damien Black, dastardly treasure hunter and master of disguise!
If Damien Black is in school, does that mean "he's "behind Ms. Krockle's absence? Could she have been kidnapped? And does that mean Dave has to rescue her? Ay chihuahua! The capped crusader is (reluctantly) on the case. "From the Hardcover edition."