- In Chapter 1, Max finds himself lured to a storage closet. This is the same closet he's shoved into later, where he finds his tool. Both Isaac and Mr. Spender have described tools as "luring a compatible spectral to them".
- Doctopi are revealed in Chapter 2 to be pain-eating spirits. This explains why Johnny didn't feel hurt after Max's scooter landed on his face in Chapter 1: a Doctopus ate all of his pain.
- Max claims that Ed threw a can at him in Chapter 2, which Ed denies. In the following chapter, the spirit residing in the bat is revealed to have magnetism powers.
- While Johnny's antics seem to be knee-jerk reactions in Chapter 3, he does have realistic motives. When he initially encounters Max and Isaac, he decides to bully them since he's still wound up from a previous fight. Then Isaac, a kid Johnny hasn't seen before, effortlessly jumps over a high fence. This sparks his curiosity, so he keeps trying to harass Max after he gets thrown near Johnny. Max then uses his bat to go flying over a fence, intriguing Johnny even more. Johnny tries to figure out how the bat works by stealing it and Max's scooter and trying to use the bat on the scooter, but this only results in him breaking the scooter. Having the scooter fly out from underneath him for seemingly no reason as well as witnessing Isaac kick lightning around are just the icing on the cake of the other weird sights he'd been exposed to that day.
- Ed is an oddball, spouting many out-there phrases. However, his advice to Max in Chapter 4 suggests that he's exaggerating his qualities to hide his spectral powers:
Oh, don't worry. Peeps won't deduce the whole spirit ghost secret spectral superpowers club thing from a bit of weird behavior. They'll just think yer crazy! And if ya really own it, they might even like you! Ha ha!
- Agent Day is a blind spectral who works for the Activity Consortium. Her tool is her cane, which fires arrows that cause the target to fall in love with the first thing it sees. This is a play on the phrase "Love is blind" or "blinded by love".
- The relationship between Mr. Spender and Mr. Garcia has very subtle hints leading up to its reveal:
- After the fiasco with the Ghost Train, Spender has company over at his house (seen as a smoking shadow in another room).
- When Spender is getting ready to meet up with Texas Walker and Boss Leader, there are two glasses and a bottle of wine on the table.
- Spender and Garcia coordinate their work outfits.
- Spender's lunch bag has a heart drawn on it.
- When Garcia compliments a lunch lady, she responds that she's not his type.
- When Max worries that a blow to the head killed Johnny, Isaac responds that there would be a ghost if Johnny was really dead. With Isaac's earlier comment that Spender tends to only teach Isaac small, contextually relevant bits of information, it's highly likely Isaac knows what he told Max because he's personally seen someone die.
- When Max is in the process of gaining his spectral abilities, he tries to push through a crowd of people in the hallway. All of these people (sans Suzy) are revealed to be ghosts. Ghosts, by nature, don't tend to last very long, although they can hang around longer if their deaths were painful. With the sheer number of ghosts in the hallway, there are two possible outcomes: Either a lot of kids suffered very painful deaths that lead to them sticking around longer, or a lot of kids died very recently.
- The Activity Club consists of 12-year olds (and a 13-year old) fighting dangerous spirits. Boss Leader mentions that she's known Spender since puberty, so it's likely that children have been forced to fight for their lives for multiple generations. Isabel and Ed in particular have been battling highly dangerous entities since they were at least 6 years old.
- In Chapter 4, Spender is warned by his spirit, Lucifer, that performing a technique known as "Spirit Fusion" would result in Lucifer being unable to keep the dangerous shadow spirit contained inside Spender. This warning comes true after Spender uses the technique anyway to catch up to the Ghost Train, with the shadow spirit covering the area in front of him, including Max and Isabel, with shadowy tendrils. One of the abilities the shadow spirit showcases is the ability to turn its shadows into bottomless chasms. Isabel later tells Max in Chapter 5 that Spender uses Spirit Fusion all the time, although she's never seen the shadow spirit before. If Lucifer's warning is describing a consistent danger, Spender has come close to accidentally releasing this dangerous, implicitly malevolent spirit from himself multiple times, in front of the children he's supposed to be protecting.
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