Steve Martin darkens his usual screwball comic persona for Novocaine, playing a suburban dentist implicated in drugs and murder charges in a noir-tinged comedy thriller which turns increasingly Hitchcockian as it unfolds. Helena Bonham Carter's femme fatale, Laura Dern's dental assistant and Kevin Bacon's hilarious cameo appearance lend extra clout to a patchy but commendably accomplished feature debut from writer-director David Atkins.