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 Ms. Duda refilled her prescription for what they wanted: narcotic painkillers.

Ms. 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 house here, trying to catch the men. Ms. 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.