Leeches (2019) Timeline Explained – Every Event in Order

The leeches fed on the college swimmers' blood, which was saturated with anabolic steroids they had been taking to enhance performance. The steroids acted as a growth catalyst, causing the leeches to mutate and grow to oversized proportions with each subsequent feeding.

Foreshadowing: The timeline notes that the leeches fed on steroid-rich blood during the lake scene, growing subtly larger before their true threat was realized.

• leeches
• steroids
• mutation
• growth
• lake scene

The coach had been infected by a leech prior to the pool confrontation. As the leech fed on him, it likely affected his behavior and cognition, causing him to attack the group and delay their electrification plan.

Foreshadowing: The timeline indicates the coach was infected before the final confrontation, and his attack directly caused the fatal delay.

• coach
• infection
• leech attack
• delayed plan

One of the surviving swim team members was revealed in the ending to have been the mastermind behind creating the leeches. This team member had been secretly breeding them in a campus lab, making them responsible for the entire outbreak.

Foreshadowing: The timeline notes the plan reflected 'desperation mixed with a scientist's curiosity,' hinting at deeper knowledge about the creatures.

• survivor
• mad scientist
• breeding stock
• creator

The leeches targeted the swimmers because their blood contained anabolic steroids. After feeding on the steroid-enhanced blood at the lake, the leeches became addicted to that specific chemical composition, causing them to return repeatedly to the source of their preferred food.

Foreshadowing: The initial lake encounter established the leeches fed on the team's drug-enhanced blood, creating an unbreakable feeding pattern.

• leeches
• swimmers
• steroids
• blood
• targeting

The leeches were washed down the campus shower drain but survived because they can survive in plumbing and dark, damp environments. From there, they continued to grow and multiply unseen, eventually emerging to feed on the steroid-using swimmers.

Foreshadowing: The timeline explicitly states the leeches survived the shower drain and began multiplying without anyone noticing.

• shower drain
• survival
• plumbing
• campus

The survivors needed a way to kill all the leeches at once. By using one swimmer as bait to lure the leeches into the campus pool, they could then electrify the water to simultaneously fry all the creatures, similar to how electric eels defend themselves in nature.

Foreshadowing: The plan involved luring leeches to a 'vulnerable target' where they could all be eliminated together.

• electricity
• pool
• killing leeches
• bait plan

The swim team used anabolic steroids to gain a competitive edge in their races. The team culture rewarded enhanced performance and encouraged secrecy about the methods used to achieve better results, creating an environment where steroid use became normalized.

Foreshadowing: The timeline notes the culture around the team 'rewards enhanced performance and secrecy' while denying potential side effects.

• steroids
• swim team
• performance
• competition

The leeches started killing after they had grown sufficiently large from feeding on the steroid-enhanced blood. Once they reached their mutated size and appetite, they returned to feed again, killing several team members and an administrator when their hunger became unsustainable.

Foreshadowing: The timeline shows the leeches grew 'subtly larger and more aggressive' after initial feeding, foreshadowing their deadly return.

• deaths
• killing
• leech attacks
• return

The ending reveals that the surviving team member who created the leeches still has breeding stock kept in the campus lab. This means the threat is not truly eliminated and could potentially restart the cycle of horror through future experiments.

Foreshadowing: The timeline explicitly notes 'breeding stock remains, hinting at the possibility of future danger.'

• breeding stock
• ending twist
• future threat
• sequel

When the infected coach attacked the survivors and delayed the electrification, the leeches used that extra time to attack and kill one more swimmer. The delay proved fatal because the leeches were actively hunting and needed only a brief window to claim another victim.

Foreshadowing: The coach's infection and subsequent attack directly caused the timing failure that led to the additional death.

• delay
• coach attack
• swimmer death
• timing