SOURCE THEATER kicks off its first "Showcase Series" with "Yeats After Life," a trio of simply staged, thematically linked one-act plays by William Butler Yeats, founder of Ireland's Abbey Theater, who was preoccupied with (bleak) visions of the world to come.

"The Cat and the Moon" combines music and masks with a quaint folk legend about two beggars -- one blind, one lame -- given the chance to choose between earthly and eternal rewards. Although the words suffer somewhat from confused dialect and overemphatic acting on the part of the beggars, the playlet benefits from Jack Guidone's extraordinary grotesque masks and rhythmic punctuation from a musical trio.

Black humor and horror mark the stark "Purgatory," in which an old man recounts his bitter life to his son as they stare at the father's ruined house. The more traditionally structured "Words Upon the Windowpane," rather dryly recreates a seance that brings back the spirit of Jonathan Swift and gets to the metaphysical heart of the revered satirist's celibacy; Yeats decides that Swift refused to beget children because of his dread of the future.

But the evening's most stirring moment belongs not to Yeats, but to his follower, Samuel Beckett. As an unadvertised bonus, Beckett's tragicomic (and typically opaque) monologue "Texts For Nothing" is antically performed by Krystov Lindquist, marvelous in macabre, dead-white makeup and rags, with counterpoint provided by a bass fiddle.

A particularly enjoyable part of the evening is the musical accompaniment throughout -- sprightly, sad and shimmering, it adds a depth and sweetly melancholy atmosphere that sometimes the actors alone can't reach. Arrive early, and you'll be treated to a delightful mini-concert.

The Showcase Series, presenting no-frills productions of deserving new and seldom-produced plays, will continue with T.J. Edwards' comedy "Busboy," winner of Source's 1984 Playwriting Contest, through March 9 at the Resource; "Homer" and "Come Sit By Me," February 20 to March 16 at the Main Stage; and "Gallows Humor," February 13 to March 9 at the Resource. Call 462-7782 for details.

YEATS AFTER LIFE -- At Source Theater Main Stage through February 16.