Lucy (Lucille Ball) tries to find out if Ricky (Desi Arnaz) is faithful by donning a black wig and passing herself off as a sexy senorita. Ricky, however, is wise to her scheme, and decides to teach her a lesson by pretending to succumb to the seductions of the "mysterious brunette." Before the situation has played itself out, both Lucy and Ethel (Vivian Vance) have donned quite a few ludicrous disguises! The plot of this episode vaguely resembles the 1940 B-movie You Can't Fool Your Wife -- which also stars Lucille Ball. ~ Rovi