Much of the film revolves around the retrieval of an object known only as The Rabbit’s Foot. But nobody discloses information about it. What was the Rabbit's foot and what could it do?
We don't know what it does, and that's sort of the point. All we know is that it's something the bad guy wants, and the good guys will prevent that from happening.
The Rabbit's Foot is a classic MacGuffin, a nebulous object of desire that drives the plot.