In Book 2 of the My Pet Slime series, Piper and Cosmo are in a race against slime! In Book 2 of the My Pet Slime series, Piper and Cosmo are in a race against slime! Piper was beyond surprised when her slime magically came to life and became her adorable pet, Cosmo. Now she must deal with an even bigger shocker: Her grandma has gone missing. With the help of their new friend Claire, it's up to Piper and Cosmo to save Grandma Sadie!