SLAVE has one problem: it it does not know what it wants to be. To classify as a thriller it is too boring and too predictable. To classify as a "torture porn" it is nowhere near graphic enough. To qualify as a serious anti-human trafficking/sex slave movie it is too tame and doesn't focus enough on the atrocities.
It is not, that the story is uninteresting, a better writer and a better director would have made the difference here. The acting - especially Natassia Malthe's performance - wasn't bad at all.
Also I found the finale rather unbelievable, ridiculous, rushed and unsatisfying.