Some time ago, before the return of the Elements of Harmony, Princess Celestia needed other heroes who could protect Equestria. She formed Equestrian Intelligence Department 6, or EI:6 for short, to hunt down and imprison dangerous monsters before peaceful folk even knew they were in danger; in time, this mandate extended to dangerous ponies as well, those who had the potential to become villains and threaten the kingdom's peace. But when they allowed a dangerous monster to escape into Equestria, Celestia shut them down.

Ten years later, Agent Sweetie Drops has found a new life in the sleepy town of Ponyville. As the innocent "Bon-Bon", she makes candies and sweets in her own little confectionery shop, living with her marefriend Lyra Heartstrings in the flat above. But only days after a bugbear attack forces her to reveal her secret, Lyra is kidnapped - by Pinkie Pie of all ponies! Finding the most special pony in her life will take a journey for Bon-Bon - and it may mean giving up her peaceful retirement forever.