Shimmerpelt is part of a border patrol consisting of herself, Duskfur, and Sneezecloud. The RiverClan cats confront Jayfeather, Alderheart, Puddleshine, and Kestrelflight, who claim that they need to speak to Mistystar, Mothwing, and Willowshine. The medicine cats tell RiverClan's patrol that they need to deliver a prophecy sent from StarClan to RiverClan's leader and medicine cats. Shimmerpelt hisses, telling Jayfeather and the others that the border surrounding RiverClan is closed, meaning no cat is able to cross it.
The silver she-cat hisses and says that there is no way she is allowing any cats to cross RiverClan's border in order to reach their camp. When Kestrelflight speaks, she curls her lip, and wants to know if WindClan has become a real Clan again. Kestrelflight brushes the comment off, and tells the RiverClan she-cat that WindClan has learned from Onestar's mistake, and that Harestar is their leader now. Shimmerpelt and the others threaten to chase Kestrelflight and the other medicine cats away, so they decide to leave without causing a fight.
When ThunderClan and WindClan cats approach RiverClan's border to collect watermint, Shimmerpelt and Havenpelt approach the patrol. The former orders them off RiverClan territory, due to their borders being closed. Sparkpelt retorts that they're on WindClan territory, and therefore don't need their permission. The RiverClan cats don't want trouble, and Alderheart suggests that he talk with Mistystar about the situation. Shimmerpelt and Havenpelt step away and discuss this, and eventually the black-and-white she-cat says he can come, but the warriors must stay behind. Sparkpelt protests, but Shimmerpelt comments that RiverClan respects medicine cats. Alderheart insists it'll be okay and travels to their camp with the two cats.
They lead him further down the stream, and keep pace while on the other side. They approach a spot in the stream with a stone in the center, and Shimmerpelt asks if this is crossable for him. Alderheart says yes and jumps across, and they walk to RiverClan's camp. Once there, Havenpelt directs the ThunderClan tom to stay put while he fetches Mistystar. The RiverClan leader agrees that they can collect watermint, but tells him to be mindful next time that her borders are closed. Havenpelt and Shimmerpelt escort him back to his Clanmates, and stand guard at the stream until the ThunderClan and WindClan cats are done gathering watermint.
When RiverClan is escaping from the fire in their camp, Softpaw is stuck in the middle of the flames. Twigpaw helps her cross the log to safety, and Shimmerpelt and Mistystar comfort the apprentice. However, the ThunderClan she-cat falls into the water, so Shimmerpelt and Mallownose swim out and rescue her. They pull her to shore, grabbing hold of her flanks.
Shimmerpelt and Reedwhisker meet Dovewing and Bramblestar on patrol. Reedwhisker yowls at the ThunderClancats to stop, but soon apologizes, remarking that he thought the cats were rogues. Dovewing thanks StarClan that RiverClan survived the flood, and Shimmerpelt replies that they had only barely. Soon after, Reedwhisker tells Mistystar that the ThunderClan cats were at their camp and Mistystar comes out to meet them.
Shimmerpelt participates in the battle against the Sisters. She fights off Furze before Sunrise calls for a retreat. At a Gathering, Squirrelflight reveals to the Clans that StarClan wants them to listen closely, and Shimmerpelt wonders if StarClan would say anything.