DENNIS, Mass. » In late April, Mildred Duda, 77, woke up in the middle of the night to find three masked men in her bedroom, rifling through her possessions. The police believe that the men had information about when Duda refilled her prescription for what they wanted: narcotic painkillers.

Duda’s home has been the target of eight attempted or successful break-ins this year, terrifying her and frustrating the police, who have spent nights stationed outside her gray home here, trying to catch the men. Duda, a retired nurse who takes painkillers for a number of ailments, including a spinal fusion and a hiatal hernia, left Cape Cod to stay with her son for the summer.

"She doesn’t even feel safe anymore," said Dan Duda, the son.

Cape Cod may be a summer playground known for its pristine beaches, shingled homes and laid-back way of life. But unbeknownst to most tourists, parts of it are plagued by drug abuse that the police say has led to a jump in property crime.

Thieves have smashed the windows of dozens of cars parked at the beach, grabbing GPS devices and iPods. Flat-screen televisions have been taken from isolated summer homes. Purses snatched out of the sand have been found in the woods, missing only cash. And while not all of the thefts can be linked to drug abuse, the police say many of those arrested for the crimes admit they wanted money for pills.

"They just tell you straight up front, ‘I’m an addict, I have a really bad Percocet problem,"’ said Sgt. Cleve Daniels of the Dennis police. Mug shots lining a bulletin board at the police department are mostly "people active in the local drug trade," he added.

In Dennis, where a gazebo with patriotic bunting sits on the town green and bicyclists in flip-flops coast down narrow roads lined with picket fences, property crime has risen sharply over the last few years, Daniels said. The number of burglaries and break-ins increased to 252 in 2010 from 122 in 2007. In the same period, larcenies rose to 396, from 256.About 75 percent of the property crimes are drug-related, Daniels estimated. Electronic signs that typically warn of road construction are reminding drivers along Route 134 to lock their cars and secure valuables.

"People come to the cape and it’s often they’re in the vacation mentality, and the last thing they think about is crime," Daniels said. "They’re unaware of the substantial problem we do have. Everyone’s guard is down when they’re on vacation, and it seems like the perfect opportunity for people to commit these crimes."

The majority of drug users here are looking for 30-milligram tablets of oxycodone and acetaminophen, known on the street as Perc 30s, said Lt. Jack Mawn of the Massachusetts State Police, who is a member of the Cape Cod Drug Task Force.

The pills sell for about $1 a milligram, but sometimes more, and the authorities believe that most are coming from Florida. Mawn said there had been a rise in prostitution — a problem virtually unheard of on Cape Cod years ago — because of the drug trade.

Mawn said that when he arrested people, he routinely asked them if anyone in their circle was not abusing prescription painkillers. "And the answer is no," he said.

Last year, thieves broke into 50 summer homes and smashed the windows of many cars at Corporation Beach, a tranquil crescent of sand often filled with frolicking families.

The crimes are straining the police force in Dennis, whose year-round population of 17,000 swells to about 75,000 in the summer. The number of police officers stays at about 40, Daniels said."It’s a struggle for us sometimes," he said.

People typically steal cash, as well as electronics and jewelry that end up in local pawn shops, Daniels said. There have been a few drug-related bank robberies on Cape Cod, and last year, a rash of break-ins where about 300 flat-screen televisions were taken.

The problem is not limited to summer. Last winter, about 50 homes in one Dennis neighborhood were broken into, Daniels said. One woman charged had 90 oxycodone pills in her bra at the time of her arrest, he added.

In Falmouth, a man recently robbed a bank to obtain drug money, said Capt. Edward Dunne of the police department there. In Harwich, burglaries increased by 67 percent from 2007 to 2010; larcenies went up by 64 percent, said William Mason, the police chief there, who added that a majority of them were committed by people trying to "supplement their income" to buy pills.

"A lot of people think Cape Cod is only busy five months out of the year and the rest of the time we roll up our sleeves and become Andy of Mayberry here," Mason said. "What we consider serious crime, felonies — those remain static year-round."

The authorities often do not have a handle on what was stolen in the off season until people return to their second homes on Cape Cod, which coincides with an inevitable rise in theft when more people are around in the summer.

The problem extends beyond Cape Cod, said Chief Carl Wolf of the police in Hazelwood, Mo., and vice president-treasurer of the International Chiefs of Police. Wolf said departments nationwide reported increases in burglaries and larcenies attributed to prescription drug abuse."In talking to police chiefs all over the country," he said, "it’s becoming a common problem."