The Clockwork are Alicorns created for one purpose. With no doubt in their creator's mind, they are going to be perfect. He can't really keep them in the open... Yet. The whole Alicorn thing was certainly iffy, but with their capabilities to morph like changelings along with their other strengths could easily be seen as a threatening forces should they have foul intentions.
Seven-Two, nickname Whistle, is an average Clockwork Alicorn with a unique whistle that none of the others can complete. He certainly has some design errors, but were those accidental? When he gets a role in being part of security for a group of interested visitors, he is assigned to some different objectives from the creator of the Clockwork Alicorns. That leads up to the big twisting adventure where he learns a lot is not quite what it seems. He must gather some important clues to discover the truth.