''Catalyst'' is a 2002 novel by Laurie Halse Anderson. The story takes place in the same universe as Halse's acclaimed novel {{Speak}}, a year after the events of that novel, and focuses on senior Kate Malone as she makes plans for college.

Kate is a preacher's daughter who excels in chemistry and is a star track athlete, with her sights dead-set on getting into the Massachusetts Institute of Technology once she graduates from Merryweather High School. She's so determined, in fact, that it's the only college she's applied to. Her getting rejected is just the tip of the iceberg, however, as soon afterwards a fire renders her neighbors - her abrasive school nemesis Teri Litch, Teri's mentally unstable mother, and her adorable toddler brother Mikey - homeless, and Kate's father arranges for Teri and Mikey to move in with his family. Kate must now struggle to deal with her rejection from MIT and a less-than-pleasant new roommate, all while maintaining her sanity.
! Provides the following examples:

* AbusiveParents: Teri's father turns out to have been abusive towards both her [[DomesticAbuser and her mother.]]
* AdultsAreUseless: Jack Malone tries [[spoiler: and fails]] to help Teri Litch and Mikey, while ignoring that his daughter may need some guidance following her rejection from MIT.
* TheAce: Kate - stellar track athlete, budding chemist, mathematics expert - in her eyes, a perfect candidate for MIT.
* BreakTheHaughty: The whole story is about Kate dealing with this and maturing from it.
* CheerfulChild: Two-year-old Mikey Litch is perpetually adorable.
* [[spoiler: ChildByRape: Mikey is both Teri's brother ''and'' her son.]]
** [[spoiler: ParentalIncest]]
* CloudCuckoolander: Betty, an elderly neighbor of the Malones and the one to take in Mrs. Litch after the fire, claims she talks to {{Jesus}} in her television. Then there's Mrs. Litch herself, a more tragic and serious example.
* TheCameo: Melinda Sordino, the protagonist of {{Speak}}, makes a brief one - just long enough for the audience to learn [[spoiler:how much better she's doing]]. Kate can't seem to remember her last name, instead calling her "Melinda Something" in the narration.
* ChildrenAreInnocent: Mikey. The biggest problem he ever ends up causing is an exceptionally filthy diaper.
* DeadPersonImpersonation: Kate pretends to be her deceased mother when she calls MIT's enrollment office to find out why she was rejected. [[spoiler: They realize who she is and wish her good luck.]]
* DisappearedDad: Teri's father is not in the picture, having died in jail after attacking his wife with a baseball bat [[spoiler: and impregnating his daughter.]]
* DropTheHammer / TrashTheSet: [[spoiler: For Teri, part of the grieving process over Mikey's death involves smashing her partially renovated house with a sledgehammer.]]
* DueToTheDead: [[spoiler: Still in shock immediately following Mikey's death, Kate and her friends stay at the Litch house after everyone else has left, lighting candles and fingerpainting the walls.]]
* HeroicBSOD: Kate's immediate reaction after receiving the rejection letter from MIT. Also [[spoiler: Teri, after Mikey dies.]] In this case the results are much more dramatic and violent.
* [[IllGirl Ill Boy:]] Kate's brother, Toby, is implied to have been plagued with respiratory problems since he was very young.
* InfantImmortality: [[spoiler:''Painfully'' averted - Mikey wanders off by himself while everyone's distracted and ends up being electrocuted.]]
* TheMourningAfter: Jack Malone, who once told someone that he buried his heart along with [[TheLostLenore his wife.]]
* NoNameGiven: Teri's mother is only ever called Mrs. Litch.
* PromotionToParent: Teri has largely taken on the role of caring for Mikey, seeing as Mrs. Litch is...not entirely there. [[spoiler: Ultimately averted - Teri ''is'' the parent.]]
* StickyFingers: Teri, who unabashedly steals (and wears) Kate's watch, and later the necklace her boyfriend Mitch gave her. [[spoiler: Mitch takes offense to this, on Kate's behalf.]]
* TheCobblersChildrenHaveNoShoes: Jack Malone's job doesn't leave much time for spending time with his daughter, leaving her to her own devices when she gets rejected from MIT. He doesn't even know that she had no safety schools. He spends more time trying to help Teri and her mother after [[spoiler: Mikey dies and Teri starts destroying her house]].
** To be fair, Jack ''does'' try to help Kate at first, before the Litches take up his attention, but Kate refuses to even talk to him about her college plans out of not wanting to admit she has no alternatives lined up.
* TeethFlying: During the fight with the football players in the school cafeteria, Teri knocks out the defensive tackle's tooth.
* [[WhatTheHellHero What The Hell Bully]]: Mitch calls out Teri for stealing Kate's things and using Kate as an emotional punching bag after [[spoiler: Mikey's death]].
** Averted, however, when Mitch finds out that Kate has no safety schools and thus not a guarantee of college in the next year. He doesn't criticize her, and [[CrowningMomentOfHeartwarming rallies her friends at a diner breakfast to help her.]]