On parent-teacher night, Hilda springs into action when she discovers David's pet rock is not what it seems.
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The episode starts with the Troll that Hilda saw just outside the walls of Trolberg in the previous episode waking up, and start looking for something. When it fails to find what it wants, it turns its attention towards the city. First the troll tries to smash through the wall, but then notices the Vittra tunnel. Over the course of two nights, it expands the tunnel (driving away the terrified Vittra) and enters the city.
That evening, it’s parents night at The Ahlberg School. As Hilda and Johanna arrive, they are welcomed by Principal Magnusson, who tells them that tonight they will unveil a statue of one of Trolbergs founders: Edmund Ahlberg, nicknamed The Troll Slayer.
The parent’s night is combined with a science fair where students can demonstrate their projects. Hilda brought the Nittens from Chapter 2: The Midnight Giant and David brought his rock collection, including the strange rock he found the previous episode. Johanna discovers Alfur stowed away in her purse, since he wanted to write a report about school life. Johanna urges him to keep a low profile.
Ms. Hallgrim opens the evening with a documentary film about the history of the school. But no sooner has it started, or the projector falls off the table, having been hit by David’s rock. Ms. Hallgrim immediately suspects Hilda to have thrown the rock, but she denies. Ms. Hallgrim locks David’s collection away to prevent further incidents. Hilda wonders why Ms. Hallgrim suspects her, thinking the teacher likes her. Frida and David however point out Ms. Hallgrim does not in fact like her, due to her often disruptive behavior. They cite three incidents where Hilda asked a question without raising her hand and at the wrong time (namely a history related question during science class), refused to participate in a troll drill since the procedure (duck under a desk, similar to an earthquake drill) wouldn't help during an actual troll attack, and was making a philosophical question that addresses a math problem involving apples after school was already over and her classmates had left. Frida fears Ms. Hallgrim even wants to have Hilda transferred to a special class for children with behavioral difficulties.
Johanna spends some time talking to Frida’s and Davids’ parents. Meanwhile, something starts moving inside the desk where David’s rock collection is. Hilda suddenly realizes the strange rock must be a Troll child, and it wakes up whenever it gets dark. This terrifies David, since bringing a Troll rock into the city is punishable by 50 years in prison if done on purpose, and 100 years if done accidentally. Hilda asks Alfur to pick the lock of the desk so they can get the Troll rock out of the school and back over the city wall before anyone finds out what happened. The situation is complicated when Ms. Hallgrim wants to talk with Johanna and Hilda about Hilda’s behavior in class. Frida distracts her by getting her parents to talk to Ms. Hallgrim.
With Alfur’s help, David gets the rock out of the desk and hides it under his sweater, but then the sun sets and the troll comes to live again. It tries to escape from David, dragging the boy along (who tries to cover up what’s happening by claiming he’s dancing). Once free, it begins to wreak havoc in the classroom, including freeing Hilda’s Nittens. Hilda, Frida and David are forced to hunt the troll throughout the school, but lose him once he enters the ventilation system.
Suddenly, the adult Troll shows up outside the school as well. Before the kids can think of what to do now, Hallgrim catches up with them again and orders Hilda to come to her office for a talk. As Johanna tries to convince Hallgrim that Hilda can be in her class, the baby troll falls into the office through the ventilation grill in the ceiling. Hilda manages to capture it. When she sees the adult troll just outside the window, she realizes it’ the baby’s mother. She stops Hallgrim from sounding the alarm (and thus cause panic), then approaches the adult troll and gives her back her baby.
United, the two Trolls leave the city, but stop long enough to smash the statue of Edmund Ahlberg. Now that she saved the school, Ms. Hallgrim allows Hilda to stay in her class.
- Trevor’s friends
- Trevor's mom
- Principal Magnusson
- Ms. Hallgrim
- Edmund Ahlberg (statue and archive footage)
- David's dad
- David's mom
- Frida's dad
- Frida's mom