Starts out with two panicked parents coming home and killing themselves. Before the mother killed herself she carved a number her son's hand. It is the vault number where some unknown terror exists.

Twenty or thirty years later a facility is being decommissioned all of the vaults are examined for any threat. The kid with the carving shows up and tells them not to open vault X, whatever it is. The vault has already been cleared, but upon a second look there is a secret compartment. When it's opened it releases an unstoppable vine or plant or something like that.