As the turtles and splinter was headed home from the battle Donnie noticed a turtle shell

As the others peaked include splinter

Splinter recognized her its his daughter nikki and she injured

Splinter: donetello bring you're lost little sister to you're lab to to tend to her wounds ill expose everything later

Donnie noded as he carefully picks up Nikki and carry her to his lab

Mikey: woah we have a sister

Raph: whoever did this to my little sister will pay for it