Such a frustrating disappointment

It's fun, it's light, [but] it has a hard time when its tries to get heavy.

Instead, you get a movie that's enjoyable enough, but leaves you feeling like it could have been much, much more.

A film with more than the usual spoiler issues. Talking about it in any detail feels akin to handing you a gift-wrapped present and saying, "I hope you like it -- It's a thriller about a diabolical secret experiment."