From CBS' official press release:

The team searches for Elena's former partner who disappears after an undercover sting operation, on Without a Trace, Tuesday, January 13.

The idea for the storyline came from Roselyn Sanchez, one of the series regulars.

The team searches for Elena's former partner, an undercover cop who goes missing after a sting.  During the investigation, Elena is forced to face the repercussions of her own past actions as she races to find her friend, on Without a Trace, Tuesday, January 13 (10:01-11:00 PM, ET/PT) on the CBS Television Network.

Without a Trace stars Anthony LaPaglia as Jack Malone, Poppy Montgomery as Samantha Spade, Marianne Jean-Baptiste as Vivian Johnson, Enrique Murciano as Danny Taylor, Eric Close as Martin Fitzgerald and Roselyn Sanchez as Elena Delgado.


Source: CBS
(Image Courtesy of CBS)