They come in the dead of night. From Potomac Highlands on the west of Aspen Hill on the east, they swoop down on defenseless curbs, looting the precious print. Then they are gone, in a swirl of burning rubber. They go by the name of da, da, da, dum, da, DUM! - The Rockville Newspaper Rustlers.

It would not be safe to say that all Rockville lives in fear of these rustlers, or even that most Rockvillians know of them. But tons of newspapers are indeed being ripped off from the city's curbs and front yards, and the city government has neither any idea who is doing it nor enough resources to stop it.

The papers, usually bundled and tied, are put out each Friday night by Rockville residents. They are picked up Saturday morning by a city truck. They are then taken to a Montgomery scrap dealer, where they are sold and recycled.

The process not only scores heavily with ecologically-minded Rockville folks, but it saves the city government from having to pay the $10 per ton it would have to pay if the papers were part of the garbage.

The city collects about $12 per ton when it sells the papers to Montgomery Iron and Metal, the recycling and scrap company. An average of 8.3 tons is picked up each Saturday, according to city manager Larry N. Blick. The resulting "take" of about $100 a week almost exactly cancels out the cost of manning and operating the city pickup truck.

"We've been trying just to break even," Blick said. "We're not in this for the money."

But someone else evidently is, and has been, according to Blick, almost, since the program was started six years ago. While paper thefts do not occur every week, Blick said, a month seldom passes without one.

Blick said he has no accurate count of how much paper is stolen per theft. But the city's average 1976 haul of 8.3 tons of newspaper per Saturday was 41 per cent below the 1975 average. "We don't know for sure that that's because of the rustlers," said Blick, "but some of it has to be."

Charles Wall, chief of the Rockville police, said newspaper rustling "certainly isn't one of my big crime problems." He called it "a real annoyance," however, and said he is trying to beef up Friday night patrols in residential areas to scare off the thief or thieves.

But that has not always proved possible, Wall said. He urged Rockville residents to notify his office at 340-7300 whenever they see someone heisting bundles.

Wall said his department has gotten good cooperation from Montgomery Iron and Metal whenever the police inform the company that there has been a newsjacking.

On one occasion, Wall said, a gang of rustlers was caught just as it was selling several tons worth. They agreed to turn their ill-gotten receipts over to the city in exchange for not being arrested. But the rustling did not end with that agreement, Wall said, and "we now need cooperation from citizens to stop this."

"It's a minor annoyance," said Blick, "and a mystery."