Complex sentence: Theresa agrees and then hurls a sonic lance through the Morrigan, killing her and in that moment, a powerful scream is heard through X-Factor HQ and Lorna is completely healed of her insanity.
Split into simpler sentences: Theresa agrees and then hurls a sonic lance through the Morrigan, killing her. In that moment, Lorna is completely healed of her insanity.