On a night flight from London to Boston, Ted Severson meets the mysterious Lily Kintner. Sharing one too many martinis, the strangers begin to play a game of truth, revealing intimate details about themselves. Ted talks about his marriage and his wife Miranda, who he’s sure is cheating on him. But their game turns dark when Ted jokes that he could kill Miranda for what she’s done. Lily, without missing a beat, says calmly, “I’d like to help.”
From there, Ted and Lily’s twisted bond grows stronger as they plot Miranda's demise, but soon these co-conspirators are embroiled in a game of cat-and-mouse--one they both cannot survive--with a shrewd and very determined detective on their tail.