He's Not Our Brother (A TMNT Fanfiction)

Leo had gone on a dangerous mission weeks before. His family and friends worry for his safety but are gladly suprised to see him waltz through the entrance of the lair, alive and well. But, something's different about him. He was acting.....weird. Everybody is blind about this fact except for his hotheaded brother, Raphael. Leo kept acting more and more different as time went on, sneaking out when everyone was asleep, calling secret "friends". What happened to the leader that they called their family?