Margin Call takes place at an unnamed major investment firm.  Eric Dale, a senior risk analyst, is suddenly laid off. Eric has been studying the numbers and he finds the firm holding a portfolio of questionable mortgage-backed securities. As he walks out, Eric slips a USB drive to Peter Sullivan, a junior analyst. Peter reviews Eric’s results  and he, too, becomes alarmed. His boss Sam Rogers concurs and it prompts the arrival by helicopter of John Tuld, the head of the firm. Tuld’s decision is to make a margin call, which is to dump the depreciated real estate securities on an unknowing public. The pressure on the traders is enormous. If they can’t unload these securities before buyers are aware of what’s going on, the firm may have to declare bankruptcy. 

David Denby, The New Yorker film critic, called Margin Call “easily the best Wall Street movie ever made.”