It is 5 o'clock on a perfect summer evening, and the only noticeable movement in front of the Kennedy Center is the flutter of the flags on the plaza. Off to the sides, 10 very large silver and blue trucks are poised for commando action.

Inside the Opera House, Mickey Berra is ready to move. Before the night is done, the 44-year-old head carpenter and his backstage army will have completed the first stages of transforming the Opera House into the laser-lit, high-tech roller rink set of the musical "Starlight Express."

The job is arduous, potentially dangerous, and it has to be done quickly -- in a five-hour shift on this night and an eight-hour one the next day. But Berra, who coordinates the "load-in" with Robert "B.J." Jackson, the production carpenter of "Starlight's" national touring company, knows he's in luck. Berra has brought shows in amid snowstorms (the New York City Ballet) and pouring rain (the Berlin Opera). This time he particularly appreciates the good weather that allows them to unload outdoors; having to back the trucks all the way into the Opera House is always an ordeal.

The set for Andrew Lloyd Webber's overscale, ear-popping rendition of the Little Engine That Could, with its undulating roller rink racetrack, computer technology and cutting-edge lighting, is a complicated one. "Starlight" not only mandated installing a roller rink floor, but also extending the set deep into the house and removing 112 seats.

"It's the element of the skate that complicates the show," explains Robert Nolan, the company manager, who has seen the set installed in London, New York, Tokyo and West Germany and on this tour. "All those productions have to reconfigure a theater. The big test is to copy the permanent installations in the sense of making the audience part of the show -- without ripping out the house."

There have been plenty of challenges in transforming the Opera House stage over the years: For John Curry's ice show, the 100-by-100-foot floor was covered with ice (as well as the emergency application of 10,000 pounds of ice cubes when the floor didn't freeze in time). For "Les Miserables," Berra had to install an untested computerized set of turntables that took up most of the stage. For the Bolshoi Opera, with four shows in repertory, 100 tons of scenery and fountains had to be suspended from the ceiling.

For this production, more than 50 stagehands hired by Berra for the load-in gradually show up to work with Jackson's 14 production people who travel with the show. The dress is casual -- shorts, jeans, work shirts, bandannas. The parade of T-shirts is a testament to other installations: the Who, "Les Miserables," the Boston Ballet.

Around 5:45 p.m., the first of the 10 trucks moves into place behind the Opera House loading doors, right on the plaza. (An 11th truck, which contained motors that had to be positioned before the load-in, preceded the company.) Ramps beneath the trucks are unloaded and assembled, and at 5:55, Berra, clipboard in hand, moves to the front.

At 6 on the dot, an army of electrical boxes, wardrobe trunks, suitcases, unidentifiable objects that look like giant Erector set pieces, electrical parts, genie lifts with rubber coils -- all on wheels -- are guided down ramps and into place. Some cartons are so heavy that it takes six people to get each one down the ramp. A 5,000-pound motor (to move the starting gate for the show's races) gets particular attention as it is guided down the ramp of a flatbed truck.

The crew members, all of whom belong to the International Alliance of Theatrical Stage Employees (IATSE) union, range in age from 20 to 60. This is an experienced local crew where everybody knows his job (or her job -- there are three female stagehands). The men tend to be muscular, if not large, and not into health foods. There is chili, not cottage cheese and salad, on the plastic foam plates from the Kennedy Center's canteen. Some people are smoking cigarettes.

"Stage employee" doesn't begin to describe the range of job skills that will be dipped into for this load-in: carpentry, rigging, plumbing, running computers, electrical work. To an observer, the atmosphere is amazingly calm and orderly. There is an occasional "Hey, George, you got a topper for this?" or "Which order do they go in?" but nobody seems to be giving orders, and nobody seems to be confused.

"If there's a problem, they just talk to the head carpenter," explains production stage manager Randall Whitescarver, referring to Jackson.

Jackson, a lanky laconic guy recently wooed away from a touring company of "Les Miserables," who expects things done "yesterday -- today at the latest," has a matter-of-fact explanation for why things are going so smoothly. "The crew already knows what to do. They're pros," he says. "You can't guess at this stuff. It only goes together one way. Once you get it up, it's a self-running show."

A great deal had already been done to prepare the 2,300-seat Opera House before the June 11 load-in. ("Starlight" continues there through July 14.) First of all, the theater had to be assessed: Would the ceiling support the 50,000-pound lighting grid the show demands? (A structural engineer had to check that out, but Berra already knew it could because of his 20 years at the Opera House. ) Would the wing width of the house mandate the small, medium or large set-up for the show? Did the loading doors open to the 10-by-10-foot space required?

Then the week before the load-in, Berra and his crew cleared the backstage area, removing much that is ordinarily left in place (such as the light pipes, the scrims, the house lights). And an advance carpenter/rigger has appeared to "spot" the placement of 36 two-ton motorized chain hoists that lift the lights, steel head blocks and the 5,000-pound motor into the air.

At the front of the house, 91 seats have been removed to accommodate the ramp for the skaters, as well as 13 for the soundboard in back and 8 for the lighting equipment on the first tier. Additional seats have been killed because of obstructed views. Subscribers whose seats were affected have been notified, and extra ushers were hired to prevent confusion.

"I try to be a coach playing ball," says Berra, who supervised the advance work with guidance from Jackson. "I know how many people it takes me to run this theater, and I figure out the right players to make the right moves."

Jackson has also told Berra how many stagehands will be needed. Berra, working with IASTRE, Local 22, has recruited them and assigned them to the various crews: carpentry (rigging and assembly of scenery); electric (lights, special effects and sound); property (seat removal, floor placement, keeping the place clean); and loaders and unloaders.

Although the evening continues to go smoothly, an underlying worry keeps the crew on edge: One of the trucks has not arrived, and it's got a piece of equipment crucial to maintaining the schedule for the night. Do they wait? Do they get depressed?

It is mostly Jackson's problem. But of course it becomes everybody's because they are all counting down to the hard and fast curtain of the first scheduled performance.

"We're always worried about whether we're going to get done on time," says Nolan. "Here I have a show where people are not sure what it is -- whether it's ice or roller skating -- and where we don't have a star. So the set and technical aspect becomes the star."

At 9:45 p.m., 15 minutes before the crew is due to quit, the truck finally arrives (and the driver peremptorily dismissed). Jackson doesn't want to quit for the night until the truss that lifts the grid loaded with lights, computer equipment and scenery into the air is assembled and bolted together as one unit. Ideally he wants "everything that flies up in the air" out of the way before the morning. That way he can put in the roller rink the next day.

Whitescarver, who knows what time he has called the cast together for a rehearsal before the first matinee, agrees. They work an extra hour to meet the revised goal and finish at 11.

By early the next morning, the doughnut-shaped roller ramp extends 44 feet into the audience; the grid is hanging up where it belongs. Fifty lights flash out into the audience and swivel around. And the crew starts to put pieces of the roller skating track in place.

By 11 the ramp has been assembled. From inside the hole in the doughnut, a computer runs through scenes from the 35mm Cinemascope anamorphic video of some of the show's skating sequences; additional lights are in place and tried out. The grid has been tied to the Opera House ceiling with spun steel aircraft cable, and the 5,000-pound motor inside it has been tied to the grid. Colored lights blink on and off "Heat One," "Race One," while a stagehand washes the floor of the starting gate that propels the skating action.

By 3, the ramp has been taped down, as have the skating tracks on the stage. Electricians hang from the grid adjusting the lights, and the back wall of the stage (where the race videos are projected) is in place.

Right on time, Berra is able to release a team of stagehands.

The following morning, the technical rehearsal has been scheduled for 10:30. The actors arrive, get their skates and warm up. At 10:40, officials from the Food and Drug Administration appear to check out the lasers that are crucial to the special effects in "Starlight's" second act. (For safety's sake, the lasers can aim no lower than six feet above the head of the patron seated on the highest level of the theater.)

By noon, Michal Fraley, the skating coach, is gliding up and down the wood tracks and ramps, checking out each crevice and curve. It is Fraley who has taught each cast member to skate. He has found that it takes a dancer about six hours to master basic techniques, and then an additional two hours a day for about six weeks to be able to handle the show. "Being on skates takes away the comfort of performing," he explains. "You know your feet and what they do, and until you regain your confidence on skates, it's unnerving."

A technician checks out sound levels. Lights blink pink, blue, aqua, yellow and rose behind the cast, which is rehearsing two of the most dangerous skating sequences in the show. The set, lights and sound pass muster, and the set is ready for the 2 o'clock matinee.

The people who have made it all come together -- Berra, Jackson, Whitescarver, Nolan -- hang around in case anything has been overlooked. At this stage of the game, a main consideration is whether the computer that creates the special effects is running properly. "During the show, you can't fix anything," Jackson says.

By opening night, the show has had one technical rehearsal and two previews. Everything is running smoothly, and Mickey Berra can take a few deep breaths. He can even take enough time off from his 65-hour work week to tidy up, put on a jacket and tie and take his wife, Marcy, to the show and cast party afterward.

"I love this business," says Berra. "Most guys never retire from it -- it's a way of life you always want to be part of. I get high on it. I wouldn't trade jobs with George Bush."