Malice Aforethought (2005)

Dr. Edmund Bickleigh is married to a particularly overbearing woman who reminds him at every turn that he is living in her house. But the good doctor has outside interests to help him cope: many of the town's female population seems to have had intimate relations with him. When a new arrival to town becomes involved romantically with Edmund, he decides maybe it was time his wife wasn't around much longer. He puts in place a plan to become free to remarry -- after all he has a cabinet full of lethal (and mostly legal) drugs on hand. But it's an old lover that proves his savior, at least for a short time.