Maude S05E22 - Vivian's Surprise

Vivian is delighted with Arthur when he returns from a trip to New England and they spend a romantic evening together. However, the next day Vivian is in for a shock, it seems Arthur has a twin brother, Arnold who has escaped from a mental institution heading to Tuckahoe to impersonate Arthur. Vivian and Maude soon realize Arnold was the one Vivian spent the night with.