As a slippery, unscrupulous home-security salesman in The Alarmist, Stanley Tucci (Big Night) brings so many surprising and delightful comic inflectionsphysical and verbalto his performance that there seems to be no limit to his expressive range. Unfortunately, director Evan Dunsky's shapeless black comedy spends most of its time following the limited David Arquette (Scream), an actor whose terminal weirdness, like Crispin Glover's, always courts embarrassment and, more often than not, achieves it. Wearing the same squinty facial contortions he uses to peddle long-distance savings, Arquette plays Tucci's shy protégé, selling alarm systems door-to-door by stoking the fears of California suburbanites. The Alarmist begins as a mild, gently ironic comment on modern paranoia and how it tends to generate peril rather than guard against it. For example, Tucci's most effective sales technique is to break into homes with existing alarm systems to convince the neighbors that they can't do without the same protection. But this slight premise, however clever, can only sustain the action for so long; like countless indie quirkfests before it, The Alarmist collapses into another vague, unnecessarily violent take on loyalty and trust. Tucci creates an inspired sad-sack, even when the movie loses interest in him, and as a widowed mother drawn to the much younger Arquette, Kate Capshaw has a modest, earthy sensuality that holds their scenes in balance. But Tucci and Capshaw aren't enough to save this low-budget patchwork.