What did Martha Stewart know, and when did she know it? Shares in Martha Stewart Living Omnimedia have dropped 10 percent today on news that FBI agents arrested Martha's longtime friend Samuel Waksal this morning. Waksal, until recently CEO of the drug company ImClone Systems, is being charged with conspiracy to commit securities fraud and perjury. According to prosecutors, Waksal tipped off two ImClone investors to sell their stock on Dec. 27, 2001—the day before the Food and Drug Administration rejected ImClone's application for a cancer drug called Erbitux. Completely by coincidence, Martha Stewart sold about 3,000 ImClone shares that very day. Stewart's shares were worth about $175,000. That's a good thing! Stewart has denied any wrongdoing, arguing that she sold because she and her broker had decided to dump if the stock went below $60 a share. Right, and I'm sure Martha personally cooks all the recipes in her magazine too. Her story is a stretch: Stewart and Waksal have been friends for years. (He dated Stewart and—ick—her daughter Alexis, according to newspaper accounts.) And congressional investigators have unearthed a message in Waksal's phone logs, dated Dec. 27, saying, "Martha Stewart something is going on with ImClone and she wants to know what."Maybe Stewart didn't get a stock tip from Waksal. Maybe her story is true, or maybe Waksal tipped someone who tipped her, and she didn't know he was the original source. But why should we have to speculate? There's a House Energy and Commerce Committee oversight hearing about ImClone on Thursday: Get Martha in there! Congress should investigate whether Martha's house needs a spring cleaning. And if Stewart won't come voluntarily, subpoena her. A warning to federal agents: Stewart is known to be armed with a glue gun.