There are a few ways that you can watch Knock at the Cabin for free. One way is to sign up for a free trial with a streaming service like Hulu or Netflix. This will give you access to their library of movies and TV shows, which includes Knock at the Cabin. Another way is to find a website that is offering the movie for free. This is usually done by illegal means, so be sure to check the site carefully before downloading anything. Finally, you can always rent or purchase the movie from a digital store like iTunes or Amazon.