Here's a more in-depth synopsis, which makes the film intriguingly sound like a horror version of Renoir's "Boudu Saved from Drowning":
"Borgman" is an allegorical tale exploring the nature of evil in unexpected places. A vagrant enters the lives of an upper-class family, igniting a descent from darkly comic dream to maddening psychological nightmare. “I wanted to show evil through the abnormal behaviour of normal people,” says Warmerdam at the film’s Cannes press conference, “the kind that you can come across in the street.”
A stateside theatrical and VOD release is planned for 2014. Fans who enroll in the "Drafthouse Alliance" subscription program can guarantee pre-order of the film.