The sun keeps shining on Omri Schein, as he plies his slightly zany, mildly campy, sometimes silly brand of branded murder mystery in theaters all over San Diego. This time, he’s back to writing and co-directing (after acting in Sherlock Holmes’ Baskerville and Hercule Poirot’s Murder on the Links). The company is the Roustabouts; the venue is Scripps Ranch Theatre, but the setting is Topsy-Turvyland: a Savoyard is a devotee of Gilbert & Sullivan’s comic operas, a form that was, at one time, wildly popular. (They even made a movie about it!) So naturally, we open with a song, as a number of people connected G&S in one way or another find themselves invited to the home of delirious devotee Tiberius Spriggs (played with almost unsettling glee by Roustabouts Artistic Director Phil Johnson). We might just have a chat/ At the soiree in his flat… But despite the occasional word juggling (“Dibble dabbles in hats!”), this is not a musical; rather, it’s a murder mystery that uses musicals for its modus operandi. Pay attention to those posters on the walls — each one designed by the host himself! It’s old-school in its ribaldry (“Ti-queerious,” “homo-cide,” “Your Nefertiti exposed too much titty!” etc.), generous with its body count, and cheerfully ridiculous. But it does provide a showcase for two notable excellences: Jennifer Brawn Gittings’ incarnadined costumes, and David McBean’s daffy and doomed array of victims. It’s always impressive to watch control in the service of crazy.