Jack abruptly reappears after being missing for weeks, only to be greeted with suspicion by the rest of the Torchwood team. Even Gwen -- newly engaged to Rhys -- feels betrayed by Jack's unexplained absence and his staunch refusal to divulge information about his past. Matters are compounded by the arrival of the roguish Captain John Hart, Jack's former Time Agent partner. John claims to be tracking three radiation cluster bombs which have tumbled through the Rift to Cardiff, threatening a planetwide catastrophe. A reluctant Torchwood splits up to recover the bombs... but John Hart is not a man who can be trusted.