The article examines how the stock market in Bangladesh reacted to the arrival of Covid-19. By studying the daily stock returns of 311 companies, the researchers found that the market responded efficiently to the news of the pandemic. They also discovered that all industry sectors were equally affected by the announcement, leading to panic selling and herding behavior among investors. These findings can help investors and analysts understand the risks in their portfolios and assist policymakers in creating strategies to deal with unexpected events.