Bess is an eleven-year-old orphan who goes from a workhouse in London to a rural cotton mill. Shocked by the horrible working conditions, she wants to go to another mill in Manchester where she hears workers are fed properly and taught to read, but she's under contract to this mill until she turns twenty-one. She and her new friend Dot plan to run away from the mill. But the mill boss warns the children of a monstrous mermaid in the pond that will eat them if they try to escape.
The Mermaid in the Millpond contains examples of:
- Bavarian Fire Drill: During Bess's first escape, she confidently walks out of the mill in full view of everyone, hoping no one will realise she isn't supposed to do that. She makes it halfway across the bridge before Miss Tucker drags her back.
- By the Hair: After Bess's second escape attempt, Miss Tucker pulls her back to the mill by her hair.
- Corporal Punishment: Children who misbehave are beaten on the backs of their legs.
- Denied Food as Punishment: After Bess's second escape attempt, Miss Tucker locks her in an old warehouse with nothing to eat or drink for an entire day. Dot is already in the warehouse as punishment for stealing food, although she managed to smuggle in some bread and butter, which she shares with Bess.
- Disappeared Dad: The book never mentions what happened to Bess's father.
- Handshake Refusal: When Bess and Dot first meet, Dot extends her hand, but Bess doesn't take it because after her ma died, she resolved not to get close to anyone again.
- It's All My Fault: Bess blames herself for her ma's death because she talked her into taking in a young homeless boy for a few days. A few months later, Ma fell ill with tuberculosis and died. Bess thinks she caught it from the boy.
- Not Evil, Just Misunderstood: When Bess tries to escape by swimming across the millpond at night, she almost gets sucked over the weir and drowned, but the mermaid pulls her to safety. Bess realises that the mermaid is trapped in the pond and wants to escape downstream, not hurt anyone.
- Orphan's Ordeal: Most or all of the workers at the cotton mill are orphans. They work long hours in an unbearably hot room with machines that can maim or kill them if they lose focus, and they aren't fed enough.
