By the time the warehouse doors slid open, the small, nondescript truck had been waiting in the predawn dark for hours, so the driver wasted little time. He loaded the precious cargo and dashed for home.

It was a scene that had all the earmarks of a thriller, but it was really just the latest manifestation of a national obsession that has seen otherwise normal Americans jam an estimated $1 billion into little slots, quarter by shining quarter, in the past year:

Pac-Man fever. It has invaded Washington homes.

The cargo of that rented truck was 3,000 Pac-Man video game cartridges, and their destination the four Evans Discount and Jewelry Stores in the area. When the shipment arrived Tuesday morning, the chain became one of the first in Washington to offer the Atari-labeled cartridges. Twenty-four hours later, all 3,000 had been sold at $29.84 apiece.

The cartridge, coupled with a $140 adapter, can convert any home television into a video arcade, allowing players to zip a Pac-Man across their screen, munching pink video wafers for points and, if the player is lucky, dodging four electronic ghosts in the process.

"We could have sold 15,000 to 20,000 that week--if we'd had 'em," lamented Tom Bothe, general manager of the Rockville-based chain. "Now we're trying like hell to get more, but it looks like it'll be another week or so."

The story is pretty much the same throughout the area, particularly in the suburbs. As fast as word spreads that the Pac-Man cartridge is for sale, the store sells out.

While sales are slightly slower in downtown Washington, the pace at which they are selling still outstrips anything else in the experience of most salesmen. It's a better seller, they say, than that well known video game, Space Invaders.

Nor does it seem to have made a lot of difference what the stores charge for a cartridge, which is about the size of a cigarette pack. Prices range from Evans' $29.84 to just under $38--not a bad profit on an item that wholesales for $23.50 apiece--and still the customers come.

"Do we have Pac-Man? We sure do. It's $34.95," Susan Isman, an employe at the Washington branch of The Math Box told one caller. The Math Box was lucky. It had about 500 cartridges left yesterday afternoon. But not for long.

"We feel sometimes like picking up the phone and just saying '$34.95' without even hearing what the customer wants to know," she said. "We've been getting about 200 phone calls a day."

A half-dozen feet away, James Hernandez, 16, and Jeff McDonald, 15, were waiting for a business-suited man, who refused to give his name, to finish playing Pac-Man so they could take a turn.

"We've already got the cartridge at home," said Hernandez, who with McDonald is a student at a nearby high school. "We've got another one on order."

"We had an Atari video cartridge unit at home but sold it," said McDonald. "Now my brother wants to buy another one just so we can play Pac-Man."

The arcade version, designed by--you guessed it--a Japanese firm, has been eating up quarters at a rate never before equaled in arcade history. Now it looks as if the simpler Atari version will bring hundreds of millions of dollars more to Atari and its parent corporation, Warner Communications.

"We're delighted," said Jeff Hoff, an Atari spokesman. In fact, so confident is Atari that they plan to have a Pac-Van featuring a larger than life Pac-Man in the April 3 Cherry Blossom Parade and are calling the date Pac-Man Day.

Sears was actually first in Washington with the cartridge but because its cartridge bears the Sears logo--it's really the same thing and is made by Atari--Evans claims it's first in the area to offer the Atari-labeled version.

Even so, demand was no different at Sears, which gave local stores about 200 of the cartridges. "As far as I know, they all sold out . . . ," said regional Sears spokesman Ted Erfer. "In the Alexandria store we had to put ropes up to keep the people orderly."

According to Dennis Hackett, salesman for suburban Maryland's D&H Distributers, supplier to some 50 Washington and Baltimore area stores, the only thing he can remember coming close to Pac-Man sales were those of CB radios more than six years ago.

"We sold 11,000 cartridges in two days to stores ," he said. "We just tell 'em we got 'em on order. What else can we do?"

All the same, Bothe believes the boom has to end soon. "After all, there are only about 150,000 Atari home video sets in the area," he said.