Castles in the Sky is set in the mid-1930s, as the storm clouds of WWII are forming in Germany. The film follows the work of Robert Watson Watt, the pioneer of Radar, and his team of eccentric yet brilliant meteorologists.
They face challenges such as a tiny budget, technical problems, and even a spy in their camp. Watson Watt also deals with marital problems as he pursues his dream.
By 1939, Watson Watt and his team successfully develop the world's first Radar system along the south east coast of England. This system proves pivotal in winning the Battle of Britain in 1940.