Zugzwang has done the impossible. He's created a spell that can defeat any lock, no matter how well protected. He demonstrates this by opening the vault at the Manehattan Bank, then opening every cell door at the local prison.

When Phillip learns that he intends to auction off the secret of the spell to the highest bidder, he has to move quick to stop him, or it means the end of security in Equestria. As long as that spell exists, nopony is safe. Especially not his friends.

The Phillip Finder series
The Pony in the Gray Trilby
The Everfree Forest Affair
Time Flies
The Blue Moon Brings Death
Letters to a Candymare
The Face in the Darkness
Checkmate
Secret of the Mare Lisa
The Sun Falls
Clockwork
Behind Locked Doors
Siege of Clovenworth
The Silent Fugitive
Curse of the Taverneigh Blue
Mystery on the Mareish Moors
The Grilled Cheese and the Muletese Falcon
Trifle Not With Monsters
The Fillydelphia Solution
The Sydneigh Ritual
Endgame