Elena, a freelance data analyst in Prague, receives an anonymous email at 3:00 AM.

Curiosity overcomes caution; Elena clicks to download the file, immediately triggering an silent alert on her workstation. 2. The Data

As she begins to decode it, Elena realizes the numbers are not currency, but geotags—coordinates—and the text corresponds to a list of decommissioned Cold War fallout shelters beneath the city [2]. 3. The Chase