Some of these pictures and descriptions may give away plot details that you might not want to know before watching the film.
This is a dark (meaning turn on some lights, please) and disturbing movie about child abduction and the extreme violence that some people are capable of.
Jake Gyllenhaal is Detective Loki who is working on a case in a suburban Pennsylvania community involving the disappearance and likely abduction of two young girls. One of the girls' fathers gets unhinged and goes vigilante - Hugh Jackman - and we have to decide if the terrible and violent things he does in trying to find his daughter were necessary and excusable. During his investigation, Loki goes to the home of a suspect where he finds a buch of locked large plastic containers with air holes in them and a heater nearby (it's winter.) He thinks the girls might be locked up in the containers so he breaks one open with a crowbar. He finds children's clothing inside that is covered with blood, and under the clothing - a bunch of snakes. That's right - a bunch of snakes - for no apparent reason other than to creep him out, and us with him. (The Norse God Loki was tortured with a snake and snake venom, but that seems like a long way to go to explain the appearance of the snakes here.) Seriously, what's up with movies and their gratuitous use of piles of snakes? Do they just assume that snakes don't require certain conditions to stay alive unlike kittens or other animals? Of course, keeping lots of snakes in boxes is not unheard of. In fact, most snake collectors and breeders store their snakes in plastic boxes poked with air holes next to heaters, but they don't pile them in together like clowns in a car.
Loki finds several containers full of snakes and they get loose and crawl over the floor and eventually crawl over his shoes until it seems he's too disgusted by the snakes to continue. (Even though they're all harmless and unthreatening.) Eventually, the police discover that the children's clothing was new, the blood was pig's blood, and the suspect was a man who had been abducted as a child who never really abducted and killed children, only store mannequins of children. That's just one of the many confusing elements of this slow, dark, overlong, and extremely violent mess.
There is another mention of snakes but it doesn't explain why we saw the snakes in the containers. The step-mother of another suspect, a young man who doesn't talk much and is described as having the IQ of a ten-year-old, explains that his condition comes from an accident he had as a boy. The only thing she says about the accident is that her husband kept snakes and the boy was afraid of them. We learn later that she's lying, and he was abducted, abused, and drugged, which probably caused his condition, but I'm left to wonder what exactly that accident was supposed to be. It's probably supposed to be believable because snakes are so horrible we don't have to even think about whether or not they could cause someone to go insane - we just know it's true.
The snakes seem to be mostly an assortment of different kinds of rat snakes and corn snakes with some other species mixed in such as a ribbon snake or garter snake.