A man drives his son toward their weekend destination. His son is bored in the backseat, playing on a phone. The son knows they're lost and tells him to call Mom because she never gets lost. The father then swerves after seeing something in the road. They end up with a flat tire. The dad sees a large, oddly-shaped rock in the road. He lifts it into the trunk and then works to change the tire. His son notices something's off as he goes to change the tire. Then when he goes to get back in the car, his son sees a shadow behind him.
Coach Lawrence gives out bags of flour, saying the kids are going to pretend they're babies. If it comes back in one piece, they pass. If it doesn't, they don't. Darci is partnered with Toby and she's worried because she needs to pass the class or she loses her mascot position. Toby says they got it. Steve comes in and smacks Toby, causing him to stab the baby with a pen. Steve tries to explain why he was late only to learn he's being paired with Eli. Jim has decorated his and Claire's flour sack. Toby takes the pen out and puts a bandage over the hole.
At a diner, Toby takes pictures of Darci and their flour baby. Darci says Logan and Mary already killed theirs by driving to give him a bath. Jim then arrives and almost leaves their baby on his Vespa. Claire and Jim argue over their flour baby. Toby wants to take their baby to a rock show, an exhibit at the museum about gems and minerals. He's had his own collection since he was eight and he's looking to get it appraised by experts. He shows off his rocks. Darci has to mascot the tacky sack semi-finals game, so she can't go. Toby says he can watch their baby. He trips and the baby goes flying, but Toby catches him. Darci thinks maybe she can fit the baby into her mole suit, but Toby promises nothing bad will happen to him. She reminds him that she needs to pass.
Claire and Jim walk home and talk about what being a parent would be like. Claire knows that she won't be like her own mother. Toby, who is walking behind them with his flour baby in a wagon, hops into the wagon and rides it like a scooter. Jim says the closest thing he had to a dad turned out to be a Changeling and tried to kill him. But at least they have parents. Claire asks Toby if he remembers his parents. He says only what Nana tells him. When Toby was two, they won the state lottery. They celebrated by going on a cruise around the world. There was a storm and they were lost at sea. Toby says Nana says they're always watching over him. Sometimes when good things happen, he likes to think it's because of them. As the walk, the shadow figure watches them from behind a pillar. As they get home, they split up for the night. Toby senses something following him and calls out for Claire and Jim. He sees the shadow-y figure in the distance, watching him. He pulls out his warhammer and screams.
Claire and Jim hear Toby and race to his aid.
When Toby swings his hammer at the creature, it oozes away. Claire and Jim appear. Jim cuts off the creature's hand, but it oozes back onto him. The creature then takes Toby's backpack and starts going through it. Claire suggests they take the creature to Trollmarket because Blinky will know what to do. Just then, a car threatens to run them over. They get out of the way and see Steve and Eli inside. After they've gone, the only thing left of the creature is his hat, which is pulled into a manhole.
Blinky, Draal, and AAARRGGHH!!! are playing a game when Claire, Jim, and Toby come in and tell them about the attack. When Blinky hears that the creature ate Toby's rock collection, he becomes concerned and asks if he had any troll remains in his collection. He admits that he had a piece of Bular. Draal says it sounds like a gruesome. They feed on the dead. He's there because Gunmar could be out. Blinky thinks it's impossible, but Toby reminds him of the blood goblins. They can investigate that later. For now, they have a gruesome to deal with. Toby tells Blinky he could be after the main course. The jewel of the collection at the museum is a large piece which Toby thinks looks like a troll arm. A guy found it outside town last week. Blinky looks at it and says it is a troll arm. He asks who would be so careless as to lose an arm. Then he looks at Draal, who says it isn't his. Jim says they need to make their stand to stop people from seeing that piece. Jim's mom calls to him and he says he'll be right up.
Gunmar is angry at the video of Stricklander. He goes to kill it, but Otto stops him and he realizes Stricklander isn't really there. The video explains that the world is different, but Gunmar says his plan stays the same. Otto says he has a spy in Trollmarket working on it. Otto is concerned with Dictatious. An advisor needs to foresee all possibilities, but Dictatious can't see anything. Dictatious then comes in and says he's had visions. His brother may have taken his eyes, but she has given him Sight. Gunmar asks what he's seen.
Blinky comes to the Museum and meets the others. He's been to RotGut's and has Dwärkstone. It's the only guaranteed way to expel a gruesome. They have to shake it to activate it and then run. They only have one chance with it.
They enter the museum and discuss their plan. Darci then comes in. The tournament ended, so she came to join them. He leads her into the exhibit while Claire and Jim split up. Claire thinks she's spotted him, but it's just a regular man. Steve spots Jim and throws the contents of his cup on him. Steve stutters and then leaves. Jim spots the gruesome entering the bathroom. He goes in and finds himself in the dark. He opens the stalls one at a time. The gruesome pops up behind him, knocking him over and knocking their flour baby to the floor. The gruesome fights him. He activates the Dwärkstone and then hides behind his shield. The Dwärkstone explodes, destroying the flour baby. The gruesome is also injured. Claire comes in and Jim tells her they need more flour. She remembers Darci and Toby's flour baby.
Jim radios to Toby, who is outside with Darci and tells him the gruesome is hurt and flour can kill it. Toby says no way, because Darci needs the passing grade. Toby snatches the baby away from Darci and runs inside with it. She tries to follow, but a guard stops her and closes the doors. Toby finds the gruesome eating the troll arm. Toby kisses Sir Isaac Gluten and approaches the gruesome. But Jim comes over the radio and alerts the gruesome to his presence. He throws the flour bag at the gruesome and watches as it solidifies and then explodes. Jim finds Toby and Toby says now he has to explain things to Darci.
Darci confronts Toby about taking Sir Isaac Gluten. Toby starts to explain, but then Claire appears with Sir Isaac Gluten, covering for Toby. Darci takes the baby and leaves. They wonder how it happened, because Claire found the baby on the floor inside. Toby looks up to the sky and thinks it was his parents.
Coach Lawrence plops Sir Isaac Gluten on the desk and says only one baby survived. He's angry with all of them. Darci and Toby are the only ones who passed. Claire and Jim think maybe Toby's parents are watching over him. Darci and Tobi leave the classroom holding hands. Jim thinks maybe, despite everything, he could be a good dad some day. Claire reminds him that he blew up their kid.
- Kelsey Grammer as Blinky
- Anton Yelchin as Jim Lake Jr.
- Charlie Saxton as Toby Domzalski
- Lexi Medrano as Claire Nuñez
- Jonathan Hyde as Mr. Strickler
- Fred Tatasciore as AAARRRGGHH!!!
- Clancy Brown as Gunmar
- Mark Hamill as Dictatious
- Tom Kenny as Otto Scaarbach
- Amy Landecker as Barbara Lake
- Cole Sand as Eli Pepperjack
- Yara Shahidi as Darci Scott
- Lauren Tom as Mary Wang
- Matthew Waterson as Draal
- Frank Welker as The Gruesome
- Thomas F. Wilson as Coach Lawrence
- Steven Yeun as Steve Palchuk
- It is revealed that Toby's parents won the state lottery and went on a cruise together around the world when he was only two-years-old, until they were lost at sea during a storm.
- Jim once considered Strickler as a father figure before he met Blinky.
- According to Aaron Waltke on Twitter, Charlie Saxton improvised the percussion-heavy tune to the "Sally Go-Back" theme song that Toby sings as he walks home, before he's ambushed by the Gruesome.
- The roleplaying game that Blinky, AAARRRGGHH!!!, and Draal play on is based off of the design of Maces and Talons from the How to Train Your Dragon franchise.
- Getting Crap Past the Radar:
- At the beginning of the episode, when swerving to avoid the troll arm, the man in the car screams "SON OF A-", in an example of a curse cut short.
- Before receiving their assignment, Mary excitedly asks Coach Lawrence if they'll be learning how babies are made.
- The closing credits feature background music similar to a lullaby played on a piano, and features photos of Toby posing with Sir Issac Gluten. In addition, when the casting credits appear, the title of the episode is revealed as "Just Add Water or (The Unexpected Life and Death of Sir Issac Gluten)"
- Running Gag: Jim, Toby, and Claire constantly misname/mispronounce the Dwärkstone as "Dork-stone".