Climb the stairs to Bill McMillan's second floor and step into a whimsical world.

Upstairs in McMillan's Midlothian home, the time is always October 1939, the place is a charming stretch of landscape between Baltimore, Md., and York, Pa., and the trains are running.

McMillan, 78, a Defense Department retiree, has transformed his finished walk-up attic into a model railroader's dream: an entire room filled with more than 85 feet of miniature track and meticulous scenery, a glorious playground for anyone who loves trains, toy or otherwise.

"It intrigued me to build detailed scenery and actually run the trains through the countryside," said McMillan. "Some people only like to run the trains, but I guess I'm a rail fan. I like to watch the trains run."

Without a doubt, McMillan and his friends from the James River Division of the National Model Railroad Association certainly have built something to watch.

They have fashioned an exquisite layout, designed to accommodate HO-scale trains. It captures the flavor of the old Maryland and Pennsylvania Railroad, 40 miles as the birds fly from Baltimore to York, but 77 miles of twisting railway that included hundreds of curves and more than 100 bridges and trestles. The layout reflects much of the actual surroundings and terrain — from blackened coal yards to shimmering creeks — as well as the bells and whistles you might expect from aficionados so devoted to model railroading.

It's amazing what one can do with some plywood, a little chicken wire and a lot of imagination. Of course, it helps to have more technical stuff, like "orthopedic gauze" that doctors use for casts but McMillan employs to cover the chicken wire for constructing rock outcroppings and such. Patience is critical, too: McMillan built one major trestle stick by stick.

The painted backdrop adds sky, clouds and even more reality. A couple of strategically placed mirrors give the impression that the tracks run forever. At various places, one can find a funeral in process, a chain gang on the job and a thriving vegetable stand with itty-bitty produce that looks good enough to eat.

Remote-control throttles control the trains drawn by vintage brass locomotives, and push-buttons bring forth music and jocularity from the world's smallest saloon and the sounds of cows and chickens from a miniature farm. Or check out the diminutive checkered tablecloths in Tom's Café, each no larger than a fingernail.

The attention to detail is astonishing yet subtle. Check out the trees, no taller than a healthy blade of grass, and notice how their autumn colors become more vibrant the farther "north" the track runs toward York. McMillan said he even walked part of the real-life rail line, picking up rocks and dirt to take home to make sure he achieved the right shades on the layout.

"It's fun," said Dr. Robert Singer, a retired neurosurgeon and a member of McMillan's crew of model railroaders who get together every other Friday evening to run the trains. Singer's specialty, as one might expect of someone with the gift of nimble fingers, is building intricate scenery. The interior of Tom's Café — the checkered tablecloths, the food on the plates, the customers at the tables — is an example of his handiwork.

"It's like I'm master of my own world," he said with a smile.

As a kid, McMillan ran Lionel trains, but he didn't become a model railroad fanatic until the early 1950s when he went to lunch with a colleague at the Pentagon. The friend stopped at a newsstand and bought a maga- zine on model railroading that he shared with McMillan.

"I read it and was absolutely fascinated," he said.

It wasn't until 1980 that McMillan began work on his layout of the Maryland and Pennsylvania Railroad, affectionately known as the Ma & Pa.

"I picked it because it seemed like a nice railroad to model, a backwoods railroad," recalled McMillan, who served for a time as superintendent of the Maryland and Pennsylvania Railroad Historical Society.

He labored on the layout for a decade in the basement of his former home in Potomac, Md., before he considered it done. Then he had to break it down when he and his wife, Carola, moved to Midlothian in 1997 to be close to their son and his family (who now live next door).

He found new partners who share his passion for model railroading and who have helped him rebuild and revise the layout. The next major project is a total rewiring of the layout to convert to digital command and control.

"As much as anything, it's a camaraderie," said Ken Montero, one of the regulars in McMillan's attic. "We just like getting together."

On a recent Friday, McMillan and five of his friends gathered. They were divided into crews, assigned specific trains and handed papers containing their "orders" for the evening. Their mission is to get their train from Baltimore to the end of McMillan's official layout at Delta, Pa., just over the Pennsylvania line, or vice versa; technically, York is "off the layout" and is depicted as a bustling railyard in McMillan's workshop on the other side of the stairs at the far end of the long, narrow room. The crews often encounter real-life railroad problems. Switching dilemmas and electrical problems occur from time to time, and then strategy becomes part of the game, which can turn the fun into head-scratching frustration.

But the dessert at the evening — on this particular Friday, chocolate cake —can always turn it back.

"I don't know whether these guys come for the model railroading or the cake," McMillan said with a smile.

Sitting around a table, eating cake and drinking iced tea on an unseasonably warm winter's evening, the talk revolved, of course, around trains.

Bill McGilvary, another regular, mentioned that he ran into a man at a national convention who had jacked up his roof and added a second story to accommodate his train layout.

"That's serious model railroading," marveled McGilvary.

Someone said they knew of other people who had designed basement layouts and built their homes on top of them.

Many of the men who have helped McMillan with his layout — and he acknowledges he could not have done it without them — have their own layouts, so they move from house to house, lending a hand to one another.

No one, though, admitted to jacking up any rooftops.

RAILROAD FANS

FOR MORE information about model railroading, visit the James River Division of the National Model Railroad Association online at http://www.jamesriverdiv.homestead.com/