Mathematician Hannah Fry pulls apart the technology sitting in everyone's pocket, tracing how contactless bank cards grew out of Cold War Soviet espionage, specifically the listening bugs planted in foreign embassies that later inspired the passive radio-frequency chips now embedded in payment cards. From there the film follows GPS back to Sputnik's launch and the Cold War military space race that eventually produced the satellite network and triangulation algorithms every phone now relies on for navigation. Fry talks through the engineering and cryptography behind everyday objects, showing how systems built for espionage and warfare quietly became consumer conveniences, often with security tradeoffs nobody notices until something goes wrong. Archival Cold War footage sits alongside demonstrations and interviews with engineers and historians, grounding the science in specific hardware and specific decades rather than abstract explanation. The throughline is unglamorous but sharp: much of modern convenience is repurposed military and intelligence technology, and the security flaws baked into that origin story are still there, just better hidden.