The Mystery Shop is a building on the US Ranch that becomes available once you reach level 14, which lets you buy and pre-order rare horses. It opened with the 2016 Chinese New Years update. You can it located next to the Quiz Stand.
The "Buy Now" option of the Mystery Shop enables players to purchase a rare horse for immediate use on their ranches. The catch is that there is a limited number of horses available, which means that pre-ordering a horse is the only true guarantee of getting it! You never know when the number will run out!
The "Pre-Order" option of the Mystery Shop enables you to buy the upcoming horse from the shop. The catch is that you won't receive the horse until it "arrives" in the store (the date will be listed in the shop). However, the discount for the Pre-Order Horse is always higher than the discount (if there is one) for the "Buy Now" horse.
- You can get Constellation Horses you might have missed with the Mystery Shop!