Cairo, the newest member of the City Spies, takes the lead when his sister disappears in Istanbul. Determined to save the family of one of their own, the team risks discovery as their search leads them to Rome. Meanwhile, there's been intel that seems to threaten the royal wedding about to take place in Westminster, bringing the team back to the UK on an official case for MI6. With so much security all over the city, it's harder than ever for the City Spies to go unnoticed. Will their skills be up to the task?