Guillermo del Toro started his trek down Nightmare Alley last week, and now Searchlight Pictures is making things official with a new synopsis and character descriptions for the film's genuinely stacked cast, headlined by Bradley Cooper and Cate Blanchett. The film, which Del Toro co-wrote with Kim Morgan, is based on the 1946 novel by William Lindsay Gresham. Here's the new official synopsis: In NIGHTMARE ALLEY, an ambitious young carny (Bradley Cooper) with a talent for manipulating people with a few well-chosen words hooks up with a female psychiatrist (Cate Blanchett) who is even more dangerous …