This story is a sequel to The Prisoner of Zebra
When Octavia's priceless cello is stolen by a greedy dragon, it's up to Flash Sentry, along with a ragtag crew of musicians, scoundrels, and special agents to get it back! Just another day's work for Flash Sentry, "Hero" of Equestria-- that is, until a certain princess gets involved ...
Volume Four of the Flash Sentry Papers.