Once Upon a Crime...

An American woman named Phoebe arrives in Rome after her Italian boyfriend, Marcello, invited her to move there. To her dismay, she finds that Marcello refuses to take her phone calls, leaving her heartbroken and alone in a foreign city.

As Phoebe wanders the streets of Rome, a dachshund wearing a stylish plaid coat snatches her lunch. After shoos the dog away, she sees a newspaper ad offering a $5,000 reward for the lost dog, setting her on a new path.

Phoebe meets Julian Peters, who has also spotted the dachshund. After a brief confrontation, the two agree to work together to claim the reward for returning the dog to its owner in Monte Carlo.

Phoebe and Julian travel to Monte Carlo by train, during which they encounter various other American travelers, including Neil and Marilyn, who discuss gambling. Tensions rise over the ownership of the dachshund as they discuss their plans.

While on the train, Phoebe encounters Augie, who claims he purchased the dachshund. Frustrated, she presses Julian to retrieve the dog, but complications arise leading to Julian reluctantly agreeing to sell the dachshund.

Upon their arrival in Monte Carlo, excitement abounds, though Phoebe is still furious with Julian's actions. Their plans to return the dog to Madame Van Dougen take an unforeseen turn as they cannot find her villa.

Phoebe and Julian stumble upon Madame Van Dougen's villa only to discover her lifeless body. Panic sets in as they realize they may be implicated in the mystery surrounding her death.

After a close call with some police officers, Phoebe and Julian opt to call the authorities anonymously. Things spiral as the police start tracing their movements and suspect them of foul play.

Meanwhile, Neil is losing all their vacation money at the casino while Marilyn wins big. Neil's gambling spirals out of control, causing further strain in their relationship.

The authorities catch up with Phoebe and Julian, thinking they are connected to the murder. With Julian arrested and police accusations mounting, Phoebe must find a way to prove their innocence.

Julian and Phoebe are taken in for questioning by Inspector Bonnard, who suspects their involvement in the murder of Madame Van Dougen. Tension mounts as they struggle to maintain their innocence.

Augie, who is also being questioned by the police, desperately tries to clear his name. His connection to the murder unfolds as the investigators gather more information from him.

Inspector Bonnard uncovers evidence that leads directly to Madame Van Dougen's housekeeper and butler as the real murderers. The revelation clears the remaining suspects and sets the stage for their release.

With the truth revealed, the group celebrates their release and newfound friendships. As they toast to the dachshund, the unexpected twists of their journey bring them closer together and leads to new beginnings.

In the final moments, it’s revealed that Madame Van Dougen left her fortune to the dachshund. Alfonso is seen enjoying a luxurious celebration with Napoleon, hinting at further twists still to come.