S3, E1: Alec travels back in time to prevent Emily's death. Kiera must follow to prevent Alec from altering history in a way that could end her chances of returning home forever. But Alec quickly sets in motion ripples that affect everyone around him - including this new timeline's already-resident Alec. Kiera arrives just in time to discover "her" Alec - now sporting a nasty scar. He's standing over another Kiera. A dead Kiera. "Scar" Alec has some explaining to do.