Abbott & Costello are American detectives working in London, and run afoul of Robert Louis Stevenson's Dr. Jekyll & Mr. Hyde in this 1953 comedy adventure.
Boris Karloff is Dr. Jekyll, but stuntman Eddie Parker, who went uncredited, was under the makeup of Jekyll's homicidal alter-ego, Edward Hyde. Chaos ensues, of course. Reginald Denny and Craig Stevens (a few years before Peter Gunn) co-star.
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Abbott, Costello, & Karloff would meet again. While this wasn't a faithful, but rather loose, adaptation of Stevenson's novel, this was by this point a by-the-numbers A & C adventure.