Sheldon Hawkes goes under water to gather clues but could be in danger when he can't come up for air. Mac learns of something else under water.

New York City has everything: Times Square, billboards, parties, and a dead model in a giant martini glass. Now the team must find a party crasher who crashed one party too many.

What would otherwise be a happy wedding goes sour when the groom... turns up dead: inside a wedding present. After Stella finds bloody puzzle pieces inside a box on her car, Mac heads home to Chicago to solve what could be the murkiest mystery of his life.

While in Chicago Mac uncovers more clues about his stalker and reveals his troubled past. Meanwhile, in New York the rest of the team is in danger. The hunt is on to figure out the identity of the 333 stalker before time runs out.