- "As harmless as they might appear, Parasites are the evil scum of the earth... and they all deserve to die."
- — The Queen of Maggots, Chapter 1
The Parasites are the main antagonists of the game. Introduced to Susan Ashworth by The Queen of Maggots, it is revealed that it is her destiny to kill them all before they hurt her or anyone else. However, Susan can choose to spare certain ones. There are 5 parasites in total.
The Parasites' appearance differ greatly from each other, but they generally look like ordinary people, usually wearing attire corresponding to their occupations.
Parasites are shown to be very deranged and ruthless creatures. Some are shown to be deceiving, whether intentional or not, making it difficult to tell one from an ordinary person. Although some have reasons for being in this state, others simply want to cause extreme pain and misery upon their victims.
A list of the Parasites, in order of appearance.
|Dr. Xavier Zelmann||Known more as Doctor X, who seems to be a calm, kind doctor/psychiatrist of the Cedar Lake Hospital. However, he shows his true intentions at the end of Chapter 2.|
|Pest Control Man||A man in a jump suit who appears to have some sign of facial hair. He is called to deal with the cats. However, he kidnaps Susan and tries to kill and eat her for dinner. He left behind a loaded revolver hoping Susan will kill herself after Gladys destroys Susan's face with bleach. His real name is never disclosed.|
|Gladys||Known more as the Pest Control Man's Wife, she appears to have a zombie-like appearance as well as wearing a bloody nurses' costume. She orders her husband what to do and is always afraid of losing him. Unlike her husband, her real name is mentioned in the credits. Her actions are revealed during Chapter 4 and she will also kill Susan if caught by her.|
|Carpenter||A mute man that appears at Susan's doorstep with flowers. His backstory is never revealed, and it appears he has no real association with Susan, or to the story, only serving as a plot device. He is never named in-game, and his only official nickname is revealed by developer Remigiusz Michalski on social media.|
| Adam||Also known as The Eye of Adam, which he uses as his screen name on the forum where he 'trolls', asking people if they have a reason for dying and telling them how to do it. He is revealed as a crippled adult male who's mother is deceased, and later kills his own father.|
- The Carpenter was originally supposed to have more of a story and a more apparent relation to Susan, however, by that point in development The Cat Lady was already taking up quite a bit of memory, and creator R. Michalski wasn't sure how to properly fit the character in, so he was forced to leave the character's backstory a complete mystery.
- The Pest Control Man's Wife, Gladys, has character portrayal similar to that of Nurse Edna from Maniac Mansion. This reference is intentional, as seen by the design of the mansion they're living in, which is similar to the titular location from the aforementioned game.
- The Pest Control Man is the favorite parasite of R. Michalski, due to David Firth being one of his favorite horror creators and loving the way Firth played the character.
- In the game Downfall, depending on player choices, Joe Davis can become the "sixth parasite" in the worse possible ending, as said by The Queen of Maggots.