The family is on a nature walk through Carls Dad Caverns, when Homer tries to get a piece from a stalactite. This results in the family falling through the cave floor and winds up with Homer getting stuck in the ceiling of one of the lower chambers of the cave. Marge, Bart and Maggie go off to find help, while Lisa stays behind and tells her father a story to pass the time. Her story involves running from a bighorn sheep and into Mr. Burns mansion. The pair evades the tenacious sheep by finding refuge in the mansions attic, where Mr. Burns tells her the story of how he came to work at Moes Tavern by losing a scavenger hunt with a rich Texan. While there he learned (and tells to Lisa) the tale of the Moes treasure. The stories within stories culminate in the fate of the treasure being determined in the cave.

As Bill prepares for the opening of a new addition to his hardware store chain, he receives bad news about his father's health, and also deals with trying to balance the needs of his three wives.

The 1998 case of a female drug smuggler is re-opened. The woman was involved with Scotty at the time he was working undercover on a high-profile drug case, and he has been keeping it a secret from the team for all these years.

A bomber strikes a Boston commuter train, leaving multiple people dead and many more injured. When the team is called in to help federal agents with the wreckage, they make a gruesome discovery-most of the casualties were children on a field trip. After Jordan takes the first wave of bodies back to the morgue, she begins the horrifying process of helping parents to identify their loved ones.

Meanwhile, Woody, Lu and Nigel search for evidence that may bring them one step closer to the bomber. Tensions run high in the morgue and in the field when Macy and Lu are reminded of painful losses from their past. Yet, there is no time to grieve, another bomb lies somewhere in the city ready to explode, and it is up to Woody and the federal agents to find it.

Carlos and Gabrielle decide to adopt, but the process comes to be a lot more difficult than either had expected. Susan finally has her surgery as she finally has medical insurance. Meanwhile, a showdown between Bree and her son Andrew lead to a full out war between mother and son. Also, a dying Noah Taylor learns more about Paul Young and his biological grandson Zach. Lastly, Tom is having more difficulty at the job when having to take orders from his boss and wife Lynette.

When Peter wins a maid for a week as a prize on a game show, Quagmire gains an interest in her, and they eventually marry. Quagmire, stricken with his bachelor ways, tries to get out of the marriage. Meanwhile, Lois stops breast-feeding Stewie, who, as a result, goes through withdrawals.

The doctors are up to their necks in their usual levels of drama. Meredith is dealing with the backlash of sleeping with George, George and Burke are bonding in ways that bother and creep out Cristina, Cristina gets stuck on diaper duty, Bailey gets involved in a case even though she's still supposed to be on maternity leave, Addison and Derek have a talk, and Izzie is still flaking on Alex for Denny Duquette, the heart patient who didn't get a heart. In the patients-of-the-week department we've got a very pregnant woman, a hockey player whose lack of concern for his injury could have dire consequences, and a woman with a fork in her neck who happens to be dying and has a struggling marriage.

Goren and Eames investigate after Trip Slaughter III, the eldest son of radio magnate Jonas Slaughter, is found dead and covered in plastic latex. Initial evidence leads detectives directly to Jonas' Chinese wife Anna, but Goren and Eames realize the evidence pointing to her is a little too pat.

While Lara is vacationing in Paris, oblivious, Dana's condition takes a turn for the worse. Alice runs into Dana's ex, Jenny introduces Max to a man from her past, Carmen evens the score with Shane, and Peggy Peabody flies to town to help her daughter. Frustrated, Bette leaves the Buddhist retreat but receives a dose of life wisdom from an unexpected source.

Tony debates on an associate's proposal to move on as he wonders how Johnny Sack's RICO trial will affect on the New York and New Jersey crime families. Meanwhile, Junior searches for some hidden treasure and Hesh decides to intervene on his son's behalf.

The candidates are surprised at their poll ratings after a close call at the San Andreo nuclear plant. Meanwhile, Bartlet debates whether or not to send U.S. troops to Central Asia to keep the peace between China and Russia in their continuing battle over Kazakhstan.

It's February and there are record temperatures of 90 degrees outside. Luckily, Jazmine has her lemonade stand open, and does pretty well. Her success catches the eye of corporate tycoon Ed Wuncler. Despite several warnings from Huey, Jazmine then learns the true meaning of "capitalism" when Wuncler decides to buy the stand.

Jonathan Ross guest hosts the comedy music quiz, with GMTV presenter Fiona Phillips, McFly's Tom Fletcher, comedian Alan Carr and Teddy Mitchell from the Mitchell Brothers joining regular team captains Bill Bailey and Phill Jupitus.