The House on Sorority Row

Vicki shot Mrs. Slater during a prank gone wrong. The sisters had planned to steal Slater's walking cane as retaliation for denying their graduation party request. Under pressure from the other sisters and possibly threatened with a gun, Vicki was holding the weapon when it accidentally discharged, striking Slater in the chest.

Earlier tension between the sisters and Slater over her controlling behavior built frustration that led to the reckless prank.

After Slater's body was concealed in the pool, an unseen figure began using Slater's own walking cane to attack partygoers. The sisters realized that turning on the pool lights would expose Slater's corpse, so they were trapped between hiding the body and stopping the killer. This created panic and prevented them from alerting authorities.

The decision to hide the body in the pool directly enabled the killer to use it as both a hiding place and a weapon.

Mrs. Slater had undergone illegal fertility treatments, which resulted in a son named Eric. This secret was never revealed to the sorority sisters or anyone at the house. Dr. Beck later explained that Slater had kept Eric hidden due to the circumstances of his birth and the traumatic events surrounding his existence.

The attic discovery of children's toys and a dead bird hinted at Slater's hidden maternal past.

Dr. Beck was the doctor who performed the illegal fertility treatments on Slater that resulted in Eric's birth. When Eric was born, Beck secretly took the child and raised him in a cage-like environment, using him for his own sinister purposes. Beck returned with the sisters not to help them but to find Eric and cover up his own involvement in the illegal procedure.

Beck's arrival at the scene seemed helpful initially but his true motives were revealed through his knowledge of Slater's secrets.

Eric was Slater's son born through illegal fertility treatments. Dr. Beck took Eric and raised him in traumatic conditions, essentially using him as a weapon. When Slater returned to the sorority house with Beck, Eric came along and began systematically murdering the sisters using Slater's cane, seeking revenge for the life of suffering he endured.

The violent nature of the attacks reflected the trauma Eric suffered at Beck's hands.

Earlier in the chaos, Vicki had used the gun to shoot Slater. After that incident, the gun was likely reloaded with blanks or never properly loaded again. When Kate tried to defend herself against Eric in the attic, she discovered too late that the gun would not fire because it contained blank ammunition instead of live rounds.

The earlier accidental shooting established the gun as an unreliable weapon throughout the film.

When Kate discovered the attic, she found children's toys and a dead bird's carcass. This revealed that Mrs. Slater had been secretly keeping items from her past, possibly relating to her hidden son Eric. The disturbing collection suggested Slater had never fully let go of her lost child and was living with the psychological weight of her secret.

This discovery foreshadowed the revelation of Slater's hidden son and her guilt over his existence.

After Vicki accidentally shot Slater, the sisters panicked and needed to dispose of the body quickly. They chose the pool because it was conveniently accessible and they believed they could control the situation. However, this decision proved catastrophic because it meant the body would be discovered if anyone turned on the pool lights, creating ongoing vulnerability that the killer later exploited.

The immediate panic and lack of a rational plan set the stage for the cascading violence that followed.

After Kate stabbed Eric multiple times with a pin, he crashed through the attic door and appeared to be dead. However, the film ends with Eric's eyes snapping open, suggesting he survived or that his spirit remains. This ambiguous, grim ending provides no closure or justice, leaving the sole survivor Kate in continued danger.

The relentless nature of Eric's attacks throughout the film suggested he would not be easily stopped.

Stevie went to the basement to cut the power after the sisters realized that turning on the pool lights would expose Slater's corpse floating in the water. Her intention was to keep the body hidden, but while in the dark basement, she was attacked and murdered by the unseen killer.

Her brave but fatal decision directly resulted from the earlier choice to hide the body in the pool.

Morgan searched Slater's room while the other sisters were looking for Slater, believing she might still be alive. In the room, Morgan discovered Slater's dead body falling from the attic hatch, revealing that Slater had been hidden there rather than in the pool as they initially thought. This discovery left Morgan vulnerable to the killer, who subsequently attacked her.

The sisters' split decision to both search for Slater and hide the body created multiple vulnerable targets.