"Busboy," at Source Theater's Resource stage, is a half-baked comedy about a scheme to assassinate the president with an explosive birthday cake. The plot quickly crumbles, suffering from underdone ideas and lapses in logic.

Behind playwright T.J. Edwards' preposterous conspiracy is an unkempt, unlikely trio of born losers: Danny Jones, a philosophy-addled eunuch; his brother Barney, obsessed with baking; and Bud, an oafish busboy who yearns to be a refrigerator repairman.

Any actor would be hard-pressed to believably play the unpleasant and incoherent character of Danny the mastermind, but Teman Treadway drew the short straw. When not rummaging through a nauseatingly overflowing ashtray, Treadway is forced to clumsily drop the names of philosophy heavies: "Guess I'll read a little Hume -- he always puts me to sleep," and "There's some Descartes I want to run over." The baker and busboy get their share of jargon as well. It all sounds as if the playwright locked himself in a room with a philosophy primer, a refrigerator repair manual, a cookbook and a leftist leaflet.

Edwards, the young actor-turned- playwright whose "N.Y. Mets" won Source's 1984 playwriting contest, exhibits an obvious concern for the underdog here -- any underdog. He seems to intend his scheming schlemiels to stand for oppressed minorities. And we are meant to find humor in these misfits' pathetic attempts to create purpose in their lives, but what laughter there is leaves a sour taste.

It seems likely that Edwards was influenced by David Mamet's "American Buffalo," which featured a similar plot about a clutch of ineffectual small-time crooks feverishly plotting a big job. Even Stephen Hayes' cluttered set, a slovenly bachelor's warren, is reminiscent of the junkshop jungle in "Buffalo." But the similarities end there. Though Edwards tries to imitate Mamet's bitterly funny vision of small men trying (and comically failing) to connect with Big Ideas, he hasn't Mamet's grasp of characters and their abuse of the language.

BUSBOY -- At Source Theater's Resource stage through February 23.