On September 15, 2008, Lehman Brothers filed for bankruptcy. It remains the largest bankruptcy filing in U.S. history, bringing a 158-year-old institution to an abrupt end. Within two weeks, AIG needed an emergency Fed bailout, and Washington Mutual became the largest bank failure in U.S. history. If you were investing back then, you probably remember how it felt. 18 years later, what happened next is worth remembering, too. In today's email: How bad things got, and how long the bad news...