Hoary but dateless hijinks in the Don Freeman mode. Ralph, an opera-loving mouse, has a diner on Pier 56. . . where, one cold and clammy night, a dark ship glides to the dock and two masked rat customers exit without paying when Ralph reads in the paper that Eduardo Bombasto (""My favorite singer""!) has mysteriously vanished. Ralph, giving chase, gets caught and thrown in the hold; opening a wiggling bag, he finds Eduardo. "" 'Who are you?' Eduardo asked suspiciously. 'I'm your biggest fan,' replied Ralph."" Then, intercepted trying to escape, the two head for the crow's nest. . . where flares are unavailing but Eduardo's singing catches the pursuing police boat's attention. It takes an all-out melee, however, to do in the rats and not only land Ralph's picture on the front page, but also get him a front-row seat for Eduardo's concert (topped off by a party on Pier 56). Broadly stroked, lightly sketched full-color pictures, strong on mood and spontaneity, and a teasing refrain ("". . . Or was it?""), also contribute to the brisk, exuberant (but unfrenzied, unmalicious) derring-do.