Complex sentence: Despite Vachon's disdain for responsibility, he tries to mesmerize Tracy into forgetting him, but finds that sheis immune to his powers; he is thus suddenly thrust into the role of her protector.
Split into simpler sentences: Despite Vachon's disdain for responsibility, he tries to mesmerize Tracy (entrance her) into forgetting him, but finds he cannot (she's immune). So, he's suddenly thrust into the role of her protector.