After a day of potion making at Zecora's hut, Apple Bloom arrives home to help Applejack plant a special tree.
However, as she does so, a petal of Heart's Desire mixes in with the dirt, affecting the seed.

The Tree of Heart's Desire grows whatever a pony wants most, but... What if what that pony wanted most was another pony? What would the creation feel, think, or even know? And how would they cope with knowing that they were nothing but a copy?