I won't recap the plot to Grim in much detail - mainly because it doesn't really have much of one. And that's a shame, as underneath the long, ponderous shots, terrible dialogue and shaky script there's a reasonable enough movie trying to get out. Unfortunately, it never does, though, leaving Grim a plodding, un-involving mess.
As a first draft or a plot synopsis, Grim's script would be acceptable in the "simple plot, let's just get on with the scares" school of horror. However, it's supposed to be a finished movie. Even the heavy-handed addition of a "Basil Exposition" character, to actually explain that the creature is a troll and explain troll-ish behaviour to the rest of the cast/viewer (i.e. they live underground, eat people, don't like light) would have been a move in the right direction.
And speaking of direction, in Grim, it's pretty woeful. There isn't a single moment in this movie that makes you jump. Not one. And, with the lackluster editing and terribly repetitive soundtrack, Grim can't be recommended.
THAT SAID, I do at least give credit to the cast and crew for trying something different. And, given the choice, I'd still take Grim over any of the Hugh Grant/Richard Curtis Rom-Coms about stuttery, up-tight Englishmen and their will they/won't they romantic complications...