Complex sentence: In "Showdown" Pt.2, Splinter finds out from Shredder, that his daughter is still alive, and when he was about to end his former friend, Karai comes to Shredder's rescue.
Split into simpler sentences: In "Showdown" Pt.2, Splinter finds out from Shredder that his daughter is still alive. When he was about to end his former friend, Karai comes to Shredder's rescue.