THE BROWNING VERSION and HARLEQUINADE, by Terence Rattigan; directed by Michael Rudman; scenerly by Carl Toms; lighting by Brian Ridley; with Alec McCowen, Geraldine McEwan, Nicky Henson, Graeme Henderson, Antony Brown, Peter Bourke, and Mary Chilton.

At the Mecahnic Theatre through June 20.

Andrew Crocker-Harris, alias "the Crock," alias "the Himmler of the Lower Fifth," would normally be a secondary character at best -- a piece of comic relief, perhaps -- in a story centering on younger, livelier, more promising figures.

After 18 years' employment at an English public (i.e. private) school, the Crock has been reduced to permanent old-fogey status, the victim of heart trouble, much snickering among his colleagues and students, and the undisguised promiscuity of his wife. In his youth, he was a brilliant classics student at Oxford, but his first few years as a teacher sufficed to rob him of the illusion that he could ever be popular or ever infect his students with his own enthusiasm for Greek and Latin literature.

Now, for reasons of health, he is about to retire, and in a final indignity his school has decided to deny him a pension (although, under similar circumstances, it awarded one a few years back to a popular teacher who had played a vital role in the success of the rugby team).

The genius of Terence Rattigan's "The Browning Version," which opened a 10-day engagement Thursday at Baltimore's Mechanic Theatre, it that it makes the Crock into a worthy hero and, incredibly, compresses the story of his life into an hour. This is an old-fashioned play, using all the tricks up a shrewd playwright's sleeve, but the net effect completely transcends the artifice and the sentimentality employed to achieve it.

The role of Crocker-Harris calls for nothing less than a great actor, and in Alec McCowen is has nothing less. McCowen makes the dry, inflexible pedantry of the character resonate with a sense of lost potential, yet his performance is acidly funny and flamboyantly theatrical at the same time. And his two costars -- Geraldine McEwan as his bitter wife, and Nicky Henson as the science teacher who has become her latest lover -- provide the kind of sympathetic, utterly professional context in which a performance like McCowen's flowers most brilliantly.

"The Browning Version" alone would represent a considerable coup for the Baltimore International Theatre Festival. But it is only half of the slightly mad package shipped across the ocean by Britain's National Theatre. After a 20-minute intermission and a startling change of scenery and costumes, the same company performs a cockeyed farce, "Harlequinade," about a -- how shall we put it? -- mature stage couple (McCowen and McEwan again) attempting to rehearse "Romeo and Juliet" in the provinces while contending with one bizarre headache after another.

Rattigan wrote the two works as companion pieces, and it is a pleasure to see the full range of the actor's art expressed in a single evening. "Harlequinade," a writer's revenge on self-centered actors, offers marvelous moments of sheer exhibitionism, and it is a particularly good showcase for McEwan's skills, which include a wonderfully lusty, husky English voice like none heard since Joan Greenwood was in her prime.

Unfortunately, Rattigan was no farceur. Most of "Harlequinade's" jokes can be seen coming over the horizon long, long before they explode, furiously and anticlimatically, on stage. Ironically, "The Browning Version," the sadder, more serious play, is the funnier play as well. But the actors have a high time in their rainbow-colored costumes and tights, and the double bill adds up to the kind of event that makes an international theater festival worth having.