A Marine is found dead under the ice of a small pond. He was involved with helping kids get out of street gangs and join the Marines. The team gets to work on finding out who was the killer.
Proof that messages were forged, was that they were longer then maximum length of message sent from cellphone, but when you try to send text message from internet/computer, same restrictions apply.
Also she mentioned 150 characters and the limit is actually 160 for SMS.