City Spies: London Calling by: James Ponti

In London Calling (Book #6 of City Spies), the stakes are higher than ever. When Cairo’s sister disappears in Istanbul, the spy team springs into action, tracing her path through Rome. At the same time, there’s a threat brewing that could ruin a royal wedding in Westminster — and the City Spies are officially called in by MI6 to help. With security tightened, secrets everywhere, and danger around every corner, can these kids out-spy the adults?