Wall Street’s semi-buoyant mood of last week turned to serious depression yesterday, with the Dow losing 381.99 points to close at 7,888.88. Investors “snapped up stocks last week in anticipation” of Treasury Secretary Tim Geithner’s new plan for banks, but he “did little to slake traders’ thirst for details” with his speech this morning, The Wall Street Journal reports, and they rushed to unload their shares. Banks were hard hit, with Bank of America dropping 19 percent and Citigroup 15 percent. The S&P dipped 42.72 points, or 4.9 percent, to close at 827.17, driven by a 10 percent drop in financials; the Nasdaq also lost 4.2 percent. Geithner’s scant specifics were “a little bit of letdown in confidence,” said the head of fixed income management at SEI Investment.