Over the past month, the SARS-CoV-2 Omicron strain has dominated world news. This fast-spreading coronavirus variant has led to travel restrictions, cancelled holiday plans, sold-out test kits, reimposed lockdowns, and of course, a staggering number of new COVID-19 cases. Scientists quickly pivoted to study Omicron, trying to learn how easily it spreads, how sick it makes us, and whether it resists our treatments, vaccines, and antibodies from previous COVID infections. We need to revisit all these questions because Omicron is very different from other coronavirus strains. Omicron has accumulated more than 50 new mutations in comparison to the strain that started the pandemic. Furthermore, Omicron is not descended from the Delta strain, which was responsible for the previous wave of infections. In fact, Omicron is so different from other variants that it seems like it’s been evolving on its own for many months. And that leads us to another mystery that scientists are puzzling over: where has Omicron been hiding while all this evolution was occurring?