Leo has been taken by Shredder and Karai and brainwashed into thinking that he is Shredder's son. Which he is actually in the world. Mikey has been hurt badly (Basically Raph in the 90s movie when he got jumped by the Foote, and both 2003 and 2012 Leo when they got jumped by the foote) and the team flee to Casey's old family house completely beaten and broken.
