Shadowseeker is first mentioned when Vanillastar is choosing cats to take to the gathering at the Glitterstones; Shadowseeker is one of the cats Vanillastar takes.
At the gathering, the glow of the Glitterstones hits Moonpaw's pelt making her more beautiful, which causes Shadowseeker fall in love with her. Shadowseeker tells Moonpaw that he loves her, mentioning that he is only a new warrior, and still young. Moonpaw apologizes to him, saying that she is waiting until she finds her soulmate, and that she believes flirting is bad. She says that when she finds the one right for her they will fall in love. Shadowseeker slinks off disappointed, and decides to flirt with Sunsetshine.