Arsenic and Old Lace recap

Drama critic Mortimer Brewster visits his charitable aunts Abby and Martha to announce his engagement to their neighbor Elaine, only to discover a dead lodger hidden in their window seat. The sisters serenely admit that they poison lonely men and have their deluded brother Teddy bury them in the cellar. Mortimer tries to contain the secret and arrange Teddy's commitment, but his murderous brother Jonathan arrives with the frightened surgeon Dr. Einstein and another corpse. Jonathan plans to kill Mortimer, while inattentive police officers repeatedly pass through the house. The police eventually arrest Jonathan, and Teddy is bound for a sanitarium with Abby and Martha choosing to join him. The aunts disclose that Mortimer was adopted, so he abandons his fear of inherited insanity and reunites with Elaine. Their final offer of poisoned wine to the lonely sanitarium superintendent suggests that the sisters have not quite retired.

In the Brewster sisters' Brooklyn home, Abby and Martha are respected for their kindness, while their brother Teddy lives upstairs believing himself to be Theodore Roosevelt. Their nephew Mortimer arrives with Elaine Harper, the minister's daughter, and reveals that they are engaged despite his career of ridiculing marriage. Looking in a window seat, Mortimer finds the body of an elderly man. His aunts calmly admit that they gave the lonely visitor poisoned elderberry wine and explain that he is not their first. Teddy has been burying the men in the cellar under the belief that they died while building the Panama Canal. Horrified, Mortimer tries to prevent another visitor, Mr. Gibbs, from drinking the wine and resolves to have Teddy committed so the cellar will not be examined after a future incident. Before he can restore order, his dangerous brother Jonathan returns with Dr. Einstein and the body of a man named Spenalzo, intending to use the same house as a hiding place.

Mortimer struggles to keep Elaine and the visiting police from learning what is in the cellar while arranging Teddy's admission to a sanitarium. Jonathan and Einstein discover the aunts' victim and realize that the household already has a larger collection of bodies than they expected. A grotesque rivalry develops between Jonathan and the sisters over their respective totals. Jonathan decides that murdering Mortimer will settle the comparison and prevent interference. The police remain oblivious: Officer O'Hara corners Mortimer to describe his long, unfinished play, consuming the time Mortimer needs to escape the danger. Jonathan and Einstein restrain Mortimer and prepare to kill him, but interruptions and Einstein's reluctance delay them. The crowded house now contains two separate criminal secrets, a deluded man digging downstairs, and officers who mistake every suspicious event for harmless Brewster eccentricity.

The arrival of Lieutenant Rooney finally changes the balance. He identifies Jonathan as a wanted criminal, and the police take Jonathan away while Einstein uses the confusion to escape. Mortimer completes the arrangements to commit Teddy, accepting that this is the only way to end the cellar burials safely. Abby and Martha refuse to let Teddy face institutional life alone and decide to enter the sanitarium with him. Mortimer, terrified that insanity and violence run through his blood, tells Elaine that he cannot marry her. His aunts then disclose that he was adopted and is not biologically a Brewster. Relieved, he embraces his future with Elaine. Mr. Witherspoon arrives from the sanitarium to finish the arrangements; when he reveals that he is a lonely bachelor, Abby and Martha invite him to sample their elderberry wine. The family crisis is outwardly resolved, though the sisters appear ready to add one last victim before departing.

The police finally recognize Jonathan as a wanted murderer and take him into custody, while Dr. Einstein slips away. Teddy's commitment papers are completed, but Abby and Martha decide that he should not enter the sanitarium alone and arrange to accompany him. They also reveal that Mortimer was adopted and is therefore not biologically related to the Brewsters, freeing him from his fear that the family's madness is hereditary. Mortimer joyfully reclaims his engagement to Elaine. As the household prepares to disperse, Mr. Witherspoon mentions that he is an unmarried man with no close family. Abby and Martha respond with renewed hospitality and offer him their prepared elderberry wine, showing that their lethal vocation may claim one final guest before they leave.