WANT TO DON a great disguise this Halloween? At the International Spy Museum, kids learn that even subtle changes in expression (furrowed brow) or clothing (lowered cap) can change their whole look. As they move through the museum's five permanent exhibits, youngsters can also see the fake hair and face-altering makeup that help spies fashion new identities for themselves.

Since opening two years ago in Washington's Penn Quarter, the museum has become a beacon for those curious about secret codes, button-hole cameras and the trench-coated folks who have shaped the course of world events. Where would we be today without World War II's Navajo code-breakers or Cold War informants? As the exhibit "The Secret History of History" makes clear, spies come in all shapes, sizes, ages and genders, from Italian lover Casanova to Confederate adventuress Belle Boyd. Indeed, real spies were just as effective as any served up by fiction. George Washington may have lacked James Bond's dash, but his intelligence-gathering efforts were key to America's victory over England. Chef Julia Child, formerly with the U.S. Office of Strategic Services, proved as dedicated and coolheaded as TV's Emma Peel, the glamorous spy played by Diana Rigg in "The Avengers." And don't let the lowly pigeon fool you. Hundreds of thousands of these birds flew secret messages across enemy lines during both world wars and earned more Medals of Honor than any other animal.

The 68,000-square-foot museum, the largest on espionage in the United States, is designed for visitors 10 and older. Younger kids may be fascinated by the idea of spying and hiding but are unable to absorb the museum's "intellectual impact," explained Jackie Eyl, manager of youth education. Older kids are more aware of both the larger, historical issues presented and the central role of intelligence in the current war on terrorism, she said.

So popular are the museum's monthly KidSpy workshops that they frequently sell out weeks in advance. Chockful of gadgets and secret codes, these programs promise action and adventure. Ex-spies -- such as museum Executive Director Peter Earnest, formerly of the CIA -- often drop in. How cool is that? But the workshops aim for more than surface wow, Eyl said. "We're not trying to create mini-spies," she explained. "We're helping kids to look at and improve those tradecraft skills relevant to their lives -- careful observation, critical thinking, analysis, teamwork." Sometimes a skill or personality trait little valued by school or peers can emerge as important during a workshop, she said. A shy kid, for example, may shine as a keen and unobtrusive observer.

Ever wanted to play spy? The museum offers ample opportunity. At the entrance, visitors assume a secret identity, build a cover and attend a "briefing" film on the nature of spying. From there, the "School for Spies" exhibit shows how spies are recruited, trained and do their work using the tools on display, including lipstick pistols and microdots (documents as tiny as punctuation marks).

Interactive displays galore help hone spy skills. On a recent visit, I noticed people crawling through simulated air ducts and scrutinizing photos on walls, pushing buttons to pinpoint suspicious activities. An especially popular computer game on disguise showed the transformation of a young, attractive blonde woman into an old, bald man with a limp. One display highlighted the work of CIA expert Tony Mendez, who spirited six American diplomats out of Iran in 1980 by having them pose as a flamboyant Canadian film crew.

A successful disguise involves "the whole body, not just the head," said Mendez, as he and his wife, Jonna, offered Halloween costume tips in a recent phone interview. These two former CIA chiefs of disguise now lead the museum's popular disguise workshop. To go with your Halloween costume, they advised changing the way you move and talk, perhaps putting a pebble in your shoe or slowing your speech, to fit your new persona. Fooling the observer involves good acting. "Imagine what you are and be that," Mendez said.

'THE ENEMY WITHIN'

Through a traveling exhibit on view through next fall, those 12 and up can enter a chilling chamber of historic fact. "The Enemy Within: Terror in America -- 1776 to Today" explores the long history of terrorism in this country. Teenagers can learn about the British burning of the White House in 1814, the Ku Klux Klan violence against African Americans throughout the 20th century and the Oklahoma City bombing in 1995. More haunting than any Halloween tale, the exhibit offers a historical perspective on recent events, including the 2001 attacks on the World Trade Center and Pentagon.

INTERNATIONAL SPY MUSEUM -- 800 F St. NW (Metro: Gallery Place). 202-393-7798. www.spymuseum.org. Open daily 10 to 8, April 1 to Oct. 31; daily 10 to 6, Nov. 1 to March 31. (Hours sometimes subject to change.) Closed Thanksgiving, Christmas and New Year's Day. Adults $13; seniors 65 and older $12; children 5 to 11, active duty military, the intelligence community and college students $10; 4 and younger free. Advance tickets recommended, especially for weekends and holidays. Advance tickets available at museum during regular hours and through Ticketmaster online at www.ticketmaster.com, at 800-551-7328 and at all Ticketmaster locations. Museum includes five permanent exhibits suitable for ages 10 and older, a 5,000-square-foot store and the Spy City Cafe, which serves sandwiches and light refreshments.

Through September, "The Enemy Within: Terror in America -- 1776 to Today," a traveling exhibit for ages 12 and older. Admission to special exhibit only: adults $5; seniors, active duty military, the intelligence community and college students $4; children 5 to 11 $3; 4 and younger free. Tickets combining museum admission and special exhibit are $17, $16, $12 and free, respectively, for categories above.

SLEEPOVERS

June 11 to 12 and Nov. 5 to 6, 2005 -- From Saturday at 6:30 to Sunday at 10 a.m., kids participate in a spy-themed sleepover, with disguises, secret covers and codes. Includes evening snack, light breakfast, photo opportunities and Sunday admission to museum. Ages 9 to 14, accompanied by adult. $115 per person. Advance registration required by calling 202-654-0930.

WORKSHOPS

Advance registration required for programs below by purchasing tickets at museum or through Ticketmaster. These fill quickly.

Nov. 13 -- From 10:30 to 12:30, interrogation workshop with former CIA analyst John Sullivan shows kids how spies seek the truth through the use of polygraph instruments. Ages 11 to 15 (no grown-ups allowed). $25.

Jan. 29 -- From 10:30 to 12:30, spy gadgetry workshop features button-hole cameras, secret listening devices and other tools of the trade. Kids can create gadgets in the Invention Lab. 11 to 15 (no grown-ups allowed). $25.

Feb. 27 -- From 10 to 4, families don disguises, perfect cover stories and set forth on adventures involving code making and breaking, surveillance and concealed devices. Ages 9 to 13, one adult required for every three kids. $75 per person.

Kids participate in the disguise workshop at an "Operation Secret Slumber" overnight program at the International Spy Museum, where they can learn about the many aspects of espionage.