Angus Shaw (Rufus Sewell), his wife Lily (Carla Gugino), and their partner Bailey (Reno Wilson) are Irish carnies who put on shows involving fake mermaids and zombies to trick rubes out of their money. One night, a customer named Mr. Woolrich (Aubrey Morris) tells them that he has a real mermaid (Rya Kihlstedt) imprisoned in a tank in his mansion. Angus decides to kidnap the mermaid and travel to America so he can get rich putting her on display, ignoring Woolrich's warnings that the creature is a killer.
She Creature contains examples of:
- Attempted Rape: The mermaid turns into a human during the full moon, leaving her weak and helpless. The sailors gang up on her to rape her, despite Lily's pleas for them to stop. Before they can rape her, she transforms into her true form - a giant amphibian monster covered in spikes - and kills all the sailors.
- Back-Alley Doctor: Lily is infertile because of a back-alley abortion during her time as a prostitute. It comes as a great surprise when she realizes she's pregnant by the mermaid.
- Burial at Sea: After Bailey's throat is ripped out by the mermaid, he is given a brief funeral service and then thrown overboard.
- Fainting: When Lily faints, Angus tells her it's because of the immense tension and stress, but it's really because she's pregnant.
- Dream Within a Dream: Lily falls asleep next to Angus and wakes up to find the mermaid ripping his throat out. Then she wakes up from the nightmare, and finds that the mermaid has eaten her hands. Then she wakes up for real.
- Glass-Shattering Sound: When the mermaid screams, the glass in the lanterns shatters.
- Mirror Monologue: Lily talks to her reflection while rehearsing how she's going to explain to Angus that the mermaid got her pregnant without sounding crazy.
- Music Soothes the Savage Beast: Used during one of Angus's scams. Bailey, pretending to be a zombie, rips free from his trick handcuffs and goes on a rampage, only to be calmed by the "singing" of Lily, who lip synchs to a record while dressed as a mermaid.
- Mystical Pregnancy: Lily eventually gives birth to a baby girl who is apparently normal except for her eyes, which sometimes turn red, like the mermaid's.
- Sole Survivor: The mermaid kills everyone on the ship except Lily, the only one of the humans who was kind to her. Lily thanks her by telling no one what happened.
