Oliver Harrington was a friend of Martha Jones.
He worked for UNIT and was stationed in Switzerland, where he worked on the Particle Collider. In 2009, he was tricked by the neutron-eating creature into believing it was his deceased wife, Marie. When he saw Martha after Torchwood arrived, he took her hostage. He next escaped into the tunnels and helped Gwen remove Ianto. Finally, he confronted the creature once the tunnels were locked. The creature revealed that it was not in fact Marie, and it only needed humans for food. In the face of his death, he told the creature that they would die together. He was annihilated by the Collider. (AUDIO: Lost Souls)