Torchwood had been conducting experiments on the breach, in an attempt to harness its energy and reduce Britain's reliance on Middle Eastern oil, but these experiments had caused the breach to widen. The "ghosts" turned out to be Cybermen from an alternate universe, which were using the widening breach to travel between universes.
Torchwood conducted tests on the breach with the goal of harnessing its energy and reducing Britain’s reliance on Middle Eastern oil, yet these efforts inadvertently increased the breach's size. The "ghosts" were discovered to be Cybermen from another universe, using the expanding breach to travel between universes.