His Ex Marks the Spot (1940) is the seventh short subject starring Buster Keaton made for Columbia Pictures.

Plot

Buster is married to his second wife Dorothy Appleby where he must pay his first wife Elsie Ames alimony leading to current financial stress. To save the alimony payment, Buster invites his first wife and new boyfriend (Matt McHugh) to live with his current wife. As you can imagine, there is a lot of comedic conflict. To get the couple out and not have to pay alimony, a shotgun wedding ensues.