As soon as twelve-year-old Steve Brixton opens a detective office in his backyard, he and his best friend Dana are caught up in a tangle of cases, from breaking up a ring of piratical smugglers, to recovering a stolen surfboard, to tracking down a fifth-grader's missing gym shorts.

In 1989 someone is threatening to steal the crown jewels, so the Queen of England summons Mac B. to England to protect them--and when they are stolen from a locked dungeon cell, where Mac and Holcroft, one of the warders, are supposed to be guarding them, it is up to Mac to figure out how they were stolen, and whether the thief is the descendant of an Irish soldier-of-fortune who tried to steal them in 1671, or someone else entirely.