Frasier receives a call on air about a woman who is convinced her husband, a German fencing instructor, is having an affair with a wealthy new client. Later, he learns from Niles that Maris has taken up fencing, with a German fencing instructor called Gunnar. Frasier is convinced that Maris is having an affair with Gunnar but Martin just says it's coincidence. However, when the caller rings back and says she has found letters describing the 'other woman' as 'not quite human woman', and reveals that her husband's name is Gunnar, Frasier is convinced. He goes to see Maris, in her sensory deprivation tank, and says that she has to end the affair and then opens it up to confront her face to face, only to find Niles sitting there. Apparently, Marta has trouble with her pronouns and so Niles is Missy Crane. Niles is determined to stand up to Gunnar and challenges him to a duel.