Tom Ward (Ben Barnes) is the seventh son of a seventh son: a rare genetic lineage that sets him on the path to becoming a Spook a.k.a., a slayer of the myriad evil creatures that haunt the land. He becomes the apprentice of grizzled, alcohol-addled John Gregory (Jeff Bridges), shortly after Mother Malkin (Julianne Moore), an evil witch, escapes her earthly prison to claim the world as her own. With only a week to go before the blood moon rises, Tom trains with Gregory but finds himself distracted by the charms of Alice (Alicia Vikander) – a mysterious young lady with a few secrets of her own.
While hardly groundbreaking in any way, the story unfolds with unexpected punch. Tom's story – one in which he comes of age and comes into his own – is accompanied by plenty of action sequences, courtesy of bone-crunching battles between men and other men (and women) who turn into soaring, swooping, fire-breathing dragons. Tom tumbles over a cliff to avoid a pursuing monster, Gregory battles a gigantic bear, and wraiths of smoke and despair trail after the Spook and his apprentice as they make their way through a dark, brooding forest.
It helps, too, that the film is leavened by a welcome bite of humour. Seventh Son doesn't take itself as deadly seriously as some of its brethren in the fantasy genre do. That's why Gregory plunges into a bar brawl armed with nothing more than his flagon of beer, and Tom is allowed to make quite a few cutting remarks about his purported mentor that are heartily returned with interest.
Ardent fans of Delaney's books should be warned: Seventh Son riffs on elements of the novels rather than staying strictly true to them. For one thing, Tom is considerably older in the film. Most noticeably, Malkin is a very different character than she is on the page. She's given more depth and complexity here, her vile behaviour explained, if not strictly justified by, her past entanglements with Gregory. It's actually quite nice to see a fantasy world that doesn't simply perpetuate the trope of the wicked witch, but instead dreams up characters that fall along a broad spectrum of morality.
Barnes is well-cast as Tom, holding his own as both a hero and quasi-romantic lead. He shares a sweet, though not particularly electric, chemistry with Vikander who is, thankfully, called upon to do more than simper and flirt. But there are considerably more thrills to be had with Bridges, who manages to fold charm, menace and darkness into Gregory; and Moore, who's clearly having plenty of fun cutting her way through scenes as a whirlwind of madness and malevolence.
By all accounts, Seventh Son should really have been an outright flop. It may still play as such to any fantasy aficionados who are demanding greatness on the level of The Lord Of The Rings. But, for pretty much everyone else, Seventh Son is an entertaining, undemanding film with some good ideas and a lot of fun moments. It's not a particularly great example of its genre but, given its troubled production history, that it's not completely execrable is probably nothing short of a miracle.