Not to be mistaken for a stage actress of that name (1890-1947), this Margaret Callahan (August 12, 1910 - November 15, 1981) was a convent-educated beauty of Irish ancestry who found herself briefly thrust into the spotlight as one of those many ornamental 1930s Hollywood ingénues. First on stage with the Stuart Walker stock company in Cincinnati, then in summer stock on Long Island, she eventually made it to Broadway in 1934 and was near top-billed in a couple of short-lived plays.

Having attracted the attention of talent scouts, Margaret was signed by RKO the following year to star in Hot Tip (1935) (an agreeable racing comedy with Zasu Pitts and James Gleason), His Family Tree (1935) (a trite farce which invoked every Irish cliche in the book and flopped at the box-office) and Seven Keys to Baldpate (1935) (another remake of the classic, featuring Margaret as Gene Raymond's love interest). Easily the best of her sextet of films (despite its title) was the detective mystery Muss 'em Up (1936), a cleverly scripted minor film noir of the Raymond Chandler/Dashiell Hammett hard-boiled school, directed with some flair by Charles Vidor. Margaret co-starred opposite Preston Foster as the gal who sends the telegram which effectively puts events into motion.