Brimstone (S01E10)

It's Christmas time and while Hetty decorates the NCIS:LA palm "Christmas tree", Callen and the team investigate the death of a Marine whose cell phone exploded in his ear.  The investigation leads them to three of the victim's fellow Marines.  They all worked with an EOD unit (Explosive Ordnance Disposal) in Iraq and all were discharged after their convoy was bombed.  When they find two other members of the team were also targets of hidden bombs, the team focuses on a fourth Marine, so disfigured in the incident in Iraq, he won't return to his family.  However, he provides a missing piece of the puzzle and refocuses the investigation on the actual killer. (CBS TV Network)