He moves back towards the window, and once again peeks out from behind the shade for signs of an impending Raph attack.

It's only when he's purposely not looking at either Leo or Don that he answer the question.

"Not long after we met April. Almost a year ago, if you don't count all the time I've spent here. Stockman's Robots attacked Splinter in the Lair while we were with April on a mission. When we got back he was gone."