Exponential

Can anything stop a creature that won't stop growing?

Sam Taylor just wants a friend. Is that too much to ask? His only mistake is finding that friend in Felix, a lab mouse that Sam rescues from the top-secret facility where he works as a janitor. Shortly after his rescue, the mouse begins to change, to swell. There's something new growing underneath Felix's fur. Growing very fast.
Holed up in a roadside bar, four survivors--a woman who's lost everything, her drug dealer, a tribal police officer, and a professional gambler--are all that stand between the rampaging beast and the city of Las Vegas. But as the monster keeps growing--and eating--how long until it's able to topple the walls protecting them?