After taking part in NATO’s operation against the Gaddafi regime in Libya, HMS Turbulent is bound for the troubled waters of the Middle East. But before she gets there, she must navigate two dangerous 'choke points'. She’s the first British submarine to pass through the Suez Canal since the Egyptian revolution, so it's a nervous moment for all concerned. And at the Bab el Mendeb Strait between Somalia and the Yemen, she must conduct anti-piracy operations, while surfaced, through the night. Meanwhile, there are new recruits to be trained for action, and Richard and Timmo both find themselves at a turning point in their careers..