Their relationship on the rocks, a young Brooklyn couple heads to a remote B&B to work things out. But from the moment they arrive at The Happy House it's one disaster after another, and they soon begin to suspect they've wandered into a real life horror movie. Events escalate from weird to terrifying as they contend with the house's batty owner, her imposing son, a moody Swedish lepidopterist, a pedantic English professor, an extraordinarily rare butterfly, the world's best blueberry muffins, a .44 Magnum, a demented serial killer, and one very strict rulebook.

After the sudden death of her husband Carl in Iraq, Katie has isolated herself from the world. One afternoon, Philip, a soldier who served with Carl, arrives at her house with letters her husband never sent her. A fragile bond forms between the two as they try to understand and cope with the loss.