Complex sentence: While he remains chained, young Tina Shepard, who witnesses her alcoholic father physically abusing her mother, unlocks previously latent telekinetic powers, resulting in her father's death at the bottom of Crystal Lake.
Split into simpler sentences: While he remains chained, young Tina Shepard witnesses her alcoholic father physically abusing her mother. Tina unlocks previously latent telekinetic powers, which results in her father's death at the bottom of Crystal Lake.