SCITUATE — Sherlock Holmes would perhaps have dubbed it “The Case of the Oviform Projectiles” and wound up baffled, but then again the great fictional detective didn’t operate in the age of the Internet.

Keith Yeaw does, however. He’s a police officer, and he has cracked an egg case.

Deputy Police Chief Stephen B. Lang gave this account:

On Oct. 11, Joyce Langlais, a retired graphic artist, emerged from her house on Riley Lane in the Hope section to discover that her car, parked in the driveway, was covered with broken eggs. Ditto the house.

“I had to hose off the roof,” she said Friday. “I’ve lived here for 50 years, but this was a first.”

Yeaw checked the neighborhood. He found three empty egg cartons on the street nearby. Then he found another house and parked car, similarly bombarded. The residents there were unaware of the vandalism until Yeaw knocked on their door. Poking around, Yeaw noticed an egg carton floating in a backyard swimming pool. It was identical to the three he had already confiscated.

The cartons came from the Hudson Valley Farms, a New York company, and all had identical universal product codes, the vertical bars read by laser-equipped cash registers.

Yeaw went back to the police station and Googled Hudson Valley, a company that supplies eggs to Walmart stores in Rhode Island.

He learned that the nearest Walmart, on Plainfield Pike in nearby Cranston, doesn’t sell eggs. But the one on Route 3 in Coventry does.

Yeaw conferred with a store security officer, who checked out the UPC number, which helps stores keep track of their sales and inventories.

“Lo and behold, at 10:25 on Saturday evening Oct. 10, two young white males purchased four cartons of eggs and they even knew what register they went through,” Lang recounted.

“A surveillance camera inside the store showed the face of one of the purchasers exiting the store,” Lang said, and an outside camera showed the pair getting into a car and driving off.

“It wasn’t good enough to see the license plate, but you could see a small, four-door silver car,” he said. “So Keith picks up the pictures from Walmart and passes them around to people in the police station. No one here can ID the boy. He proceeds to Scituate High School and checks with the school resource officer, Sgt. Kevin Pendergast. Pendergast IDs the boy as a student. In the parking lot of the school Pendergast shows the car he drives — same make, model, color as the surveillance photo.”

Since the suspect was a juvenile, Lang said, Yeaw set up a meeting with his parents.

“He confesses, and he gives up two other juveniles, like a domino effect,” Lang said. He said the culprits said they chose targets at random.

Three juveniles and one adult student, Michael A. Mariorenzi, 18, of 53 Robinwood Drive, wound up charged with vandalism, a misdemeanor. The case against the juveniles will be heard by the town’s Juvenile Hearing Board.

Mariorenzi is scheduled for arraignment Nov. 4 in Kent County District Court.

“I didn’t even know Keith was doing this,” said Lang. “He came into the office and showed me. It was an awesome investigative job, an incredible piece of investigative work — who would have thought of that? This is the first time I’ve seen this done in this P.D.”

tmorgan@projo.com