Who finds an urn in Paul's apartment?
Larry Lipton and his wife Carol meet their older neighbors Paul and Lillian House in the elevator in a pleasant encounter. But the next night, Lillian is found to have died of a heart attack. The Liptons are surprised by the death because Lillian seemed so healthy.
The Liptons are also surprised by Paul's cheerfulness so soon after his wife's death. Carol becomes suspicious and starts to investigate, even inventing an excuse to visit him. An urn she finds in Paul's apartment contradicts Paul's story that Lillian had been buried. Larry becomes frustrated with Carol, telling her she's "inventing a mystery".
Carol sneaks into Paul's apartment while he's away and finds more telling signs. Lillian's urn is missing, there are two tickets to Paris and hotel reservations with a woman named Helen Moss. Carol calls Ted, a close friend who agrees with Carol's suspicions and urges her to keep snooping. When Paul returns unexpectedly, Carol hides under the bed and overhears Paul's conversation with a woman whom she suspects is Helen Moss.
Later, Ted tracks down where Helen Moss lives, and with Carol and Larry, they follow her to a theater owned by Paul. They discover that Helen is a young actress. The three eavesdrop on Paul and Helen talking about money.
A few days later, Carol spots a woman who's a dead ringer for the supposedly dead Lillian House on a passing bus. Upon Larry's suggestion that Lillian has a twin, Ted investigates but finds Lillian has none. Larry and Carol trace this mystery "Lillian" to a hotel and, under the pretense of delivering a personal gift, they enter her hotel room, but find her lying dead on the bedroom floor. They call the police, who subsequently find no trace of the dead body.
Carol