Emma is 12, Lea is her best friend, but she finds herself on the side of Lucy when it comes to a disagreement at school. Things start to become odd in Emma's life when a strange woman appears one night. In 1944, MI5 agent, Meg has to work out who is trying to wreck Operation Neptune, the D-Day landings. Agent Snow, has given her the job of investigating three fellow spies, Agents Rain, Hail and Cloud. Emma and Meg find themselves flung together in both time periods, to work together to try to save one of the greatest plans in Second World War history. Will they be able to crack the coded messages? Will they be able to find the traitor? And why does Emma's Nan seem to know so much about it all? Emma's friendships with Meg and at school are put to the test as D -Day approaches.