Lucas finds the past catching up with him after his former Russian prison torturer, Oleg Darshavin, shows up with intelligence about a Sudanese terror attack on London. Harry and Ros aren't willing to pay the price that Darshavin wants for the information. Harry and Ros reluctantly agree to let Lucas meet with Darshavin. Lucas comes close to getting the information out of Darshavin but the arrival of CIA officer Sarah Caulfield puts the whole thing in jeopardy. After getting the name of the terrorist, Section D track him down but he is murdered before Ros can question him. Darshavin ends up being the only person left who can help the team. Harry works out that they have a traitor working within the team.