Barbie: The Mystery of the Missing Stallion (Barbie Mystery Files, #4)

(From the back cover)

Trouble at Star Canyon Ranch...

Barbie and her friend Teresa are headed to a dude ranch for Barbie's most exciting assignment yet. She's going behind the scenes of a new movie for an interview with the star, heartthrob Matt Carson.

But no sooner does she arrive at the set than the movie's other star, the champion racehorse Orion, disappears without a trace. It seems like everyone had a motive for wanting the horse out of the picture. Can Barbie find the thief in time to save the movie - and the missing stallion?