This was a fun ride that does an interesting trick of subverting the formulaic thriller you think it will be, by cramming in about two film's worth of reversals, while still kind of being that formulaic thriller.

Rachel McAdams plays Linda Liddle, a disgruntled office worker, passed over for a promised promotion by her new boss, Bradley (Dylan O'Brien). When their business trip to Thailand ends in a devastating plane crash, they are the only two survivors, left stranded on a seemingly deserted island.

Although Bradley is the boss back home, on the island it is Linda who is in charge. An obsessive fan and would-be star of the TV show Survivor, she has taught herself how to make fire, build a shelter and hunt for game and she quickly becomes the island's apex predator. Bradley, meanwhile, flounders and while he eventually shows some gratitude to his new savior, he begins to suspect that Linda is enjoying castaway life a little too much.

What starts out as a standard battle of the sexes conflict between the capable Linda and the whining and entitled Bradley soon develops into something darker, as he makes a doomed attempt to abandon her, then darker still as she exacts her revenge and we slowly learn that she hasn't been entirely honest about their predicament.

Along the way, Raimi uses his horror expertise to show just how bloody and gory things can get when you trap two individuals on an island with just one knife but lots of creativity and desperation.

Send Help can be a tough watch at times if you don't normally enjoy horror but, like the best horror flicks, it hides a pitch black sense of humour and will keep you guessing until the end.