A jealous husband’s worst suspicions are realized when he decides to test his wife’s fidelity in Enter the Guardsman, opening this week at Northlight Theatre. Based on a comedy written by Ferenc Molnar for the husband-and-wife team of Alfred Lunt and Lynn Fontanne, this backstage romp set in 1930s Vienna is a musical within a play. Hollis Resnik plays the wife; David New is the fate-tempting husband who sends her a rose from an anonymous admirer and then raises the stakes, using his thespian skills to see if she’ll cheat. When she does, he’s in a worse quandary than when he started: Did she see through his disguise, or didn’t she? Enter the Guardsman is the work of a contemporary theater couple–writer Scott Wentworth and lyricist Marion Adler–with music by Craig Bohmler. Peter Amster directs. Previews run from December 6 through December 12, Tuesday through Saturday at 8 and Sunday at 3 and 7; preview tickets are $30 to $34. Regular performances continue through January 7; tickets are $32 to $45. Call the box office at 847-673-6300 for times. Northlight is located in the North Shore Center for the Performing Arts in Skokie, 9501 Skokie Blvd., Skokie.