Two people are shot and killed with a gun that was printed from a computer, and Jo tries to uncover the identity of an anonymous philanthropist who is giving away millions of dollars to random New Yorkers.
The team tries to figure out who killed a pick-pocket who fell from a building balcony onto a car, and Jo gets a visit from a man who has shocking news related to her dead sister.
With the help of D.B. Russell from the Las Vegas crime lab, Mac is able to identify the people who kidnapped Christine. But will he get to her before it's too late?