Hercule Poirot

HarperCollins’ William Morrow division will launch Witness, a digital-first imprint for mysteries and thrillers, this October, the company announced Tuesday. Witness is part of HarperCollins’ “Impulse” line of books, which also includes digital-first romance, sci-fi/fantasy and young adult books.

The idea behind digital-first lines is that they let publishers take a chance on unknown or new authors…