Abandoned for more than 30 years, the secret military facility D4 is hidden deep in the mountains and does not "officially" exist but remains the focus of conspiracy theories. A wealthy doctor believes her son is being held somewhere in the long deserted government buildings and she has no idea why the government would kidnap him. But with no expense spared, she hires a crack team of Special Ops mercenaries to search out her son and rescue him. Once inside they discover things are not what they seem as there is someone, or something, still inhabiting D4 and, as they become the hunted, all hell breaks loose and the secrets of D4 are agonisingly revealed. What was meant to be a simple search and rescue turns into a fight for survival.