Based on a Sundance-approved short film from Nicholas McCarthy, The Pact does a valiant effort of extending its admittedly familiar premise to fill almost 90 minutes. Some of it works wonderfully, with finger-chewing levels of suspense achieved at various points and a capable leading lady in Caity Lotz  (Mad Men, Death Valley), but it becomes abundantly clear around the half-way mark that there isn’t enough story to fill the time, no matter how many times the film can make you jump out of your seat.

The premise, again, is a familiar one. Lotz’ heroine returns to her childhood home to look for her missing sister, who had already gone back a few days earlier. The reason for both their visits was the recent death of their mother, whom we’re informed mistreated them in some way when they were younger, and the ill-feeling circulating around the family sets us up for some nifty revelations later on. The sister left behind her daughter, being looked after by family friend Liz, and it’s after she goes missing during the night that Annie begins to investigate.

We’re aware from the beginning that there’s something supernatural going on, but the film uses a mixture of paranormal scares and real-life horror to set the creepy tone. The teaser starts us off slow, employing the ‘look behind you’ method when a video chat signals all is not well. And that’s where The Pact excels, using old-fashioned scare tactics but updating them to achieve some level of realism in a genre prone to stretching believability. Later on, a creepy photograph is enlarged and panned over, revealing more and more each time it is scrolled over. At one point, Annie even manages to solve the mystery just by googling serial killers in her area. It’s what we’d all do, so gets most of us on side straight away.

The tagline for the film is ‘some doors should never be opened’, and there’s certainly a good share of those in Annie’s creepy childhood residence. Besides the ghastly decor and layout, there seems to be more slightly open doorways and rooms in the house than your average suburban set-up. Due to the way the first half of the film is shot, there are doors we weren’t sure if we saw before, and they disappear just as quickly. Later, a secret room is discovered, and that’s only the start of uncovering the family secrets that make up The Pact’s big reveal. But suggestion and shadowy apparitions soon make way for short, sharp shocks, and it loses some of its power during the faster-paced second half.

Even if The Pact is an uneven film that botches its big resolution somewhat, it’s still a frequently creepy horror sure to keep you entertained while home alone. Annie makes some surprisingly good decisions during the film, all too rare for a horror heroine, and the ‘family secrets’ sub-genre is over-familiar one simply because it works so well. Even though the biggest scares here probably won’t stay with you for long afterwards, they will surely keep your adrenaline pumping for the suitably diminutive running time.