Jeff Bridges plays Master Gregory, the last of the "Spooks" - an order of knights who deal with supernatural problems. In his youth, he imprisoned (but didn't kill) Mother Malkin (Julianne Moore), a particularly powerful witch. And now she's back. He loses his first apprentice (Kit Harington) to her shortly after the credits, and goes to recruit Tom Ward (Ben Barnes) who is the seventh son of a seventh son, and thus magically gifted.
Bridges looks like someone told him "do Rooster Cogburn, but funny! And stick your lower jaw out the whole time." He's unbelievably awful. Moore, Alicia Vikander, and Olivia Williams are all good actresses, but they phoned it in - with the ironic side effect of making Barnes, a significantly poorer actor, actually look like he's doing a good job. (He's better than he was in "Prince Caspian" or "Dorian Gray," but he still has a long way to go.) It's a big budget American movie, so of course the effects are excellent. And the story - if it weren't for the appalling acting - could have been okay. I kind of enjoyed it, but it's pure tripe.