They call it a triple threat: as the director, co-writer (with her husband, mumblecore icon Mark Duplass) and star of this low-budget, female fronted survival slasher, Katie Aselton is making a concerted bid for glory. It’s a solid rather than spectacular effort, low on ambition but efficiently constructed and very watchable. Aselton is Abby, who travels with her dysfunctional old pals Sarah (Kate Bosworth) and Lou (Lake Bell) to the island of Black Rock, scene of many a youthful rampage. But when a gang of ex-soldiers crashes the party, things turn ugly, fast. Aselton walks the line between exploitation and feminist reversal with abandon: one scene of stark naked Amazon-warrior aggression veers between laughable and unsettling. The script contains a handful of effective surprises, but it’s hamstrung by the generic setup: once the gloves come off, the remainder of the plot – one woman finds her inner strength and fights back – is inevitable. ‘Black Rock’ is never dull, but it’s hardly the attention-grabbing calling card its creator presumably intended.