The series revolves around Dexter (voiced by Christine Cavanaugh in seasons 1–3; Candi Milo in seasons 3–4) a bespectacled boy-genius who possesses a secret laboratory hidden behind a bookcase in his bedroom. The laboratory is filled with Dexter's inventions and can be accessed by speaking passwords or by activating hidden switches on Dexter's bookshelf (e. g. pulling out a specific book). Though highly intelligent, Dexter often fails at what he sets out to do when he becomes overexcited and makes careless choices. Although he comes from a typical American family, Dexter speaks with a thick accent of indeterminate origin. Christine Cavanaugh described it as "an affectation, [a] kind of accent, we're not quite sure. A small Peter Lorre, but not. Perhaps he's Latino, perhaps he's French. He's a scientist; he knows he needs [a] kind of accent. " Genndy Tartakovsky explained, "he's a scientist. All scientists are foreign and have accents. . . It's not really a German accent. It's just Eastern European. "