When one of Tony's old cases ends up re-opened, he switches roles with Gibbs to finally solve the crime.

Last week, the Top 36 semi-finalists were revealed to the nation and were separated into three groups of 12. Tonight's episode features performances by the first 12 contestants, and America will vote on their favorites. Performing Tonight Is: Alexis Grace Ann Marie Boskovich Anoop Desai Brent Keith Casey Carlson Danny Gokey Jackie Tohn Michael Sarver Ricky Braddy Stephen Fowler Stevie Wright Tatiana Del Toro

It's the 100th episode of The Biggest Loser, and this week, a balancing competition will bring the winner a coveted prize a 24-hour visit from a loved one back home. Then the teams all take part in a tough challenge that tests their endurance, and later, one player will be sent home from the team that falls below the dreaded yellow line.

Rachel gets back into the dating game.

Mike enjoys his 200th dirty job by restoring locomotives in Boise, Idaho.

The murder at a country club is investigated by the CBI team.

When the unveiling of a reconstructed dinosaur skeleton at a gala event reveals the dead body of a young man found in its jaws, Murdoch must enter the world of bone-hunters to find the culprit.

Benson and Stabler investigate the case of a man who was found in the parking lot of a strip club, badly beaten and with no memory of how it happened.

Christian relates to a patient with a unique condition whilst Sean pursues a new relationship.

A woman and her infant go missing after she attends a self-defense class. The team tries to determine if any foul play is involved.

The Leverage team plots to steal Nate's former employer's CEO's prized Michelangelo maquette and sell it back to him as its twin. However, the team does not bank on a reappearance by Sterling.

Leslie discovers his great, great, great grandfather was a Native American and decides to make contact with the local Shawnee Indian tribe in an attempt to connect with his heritage. Of course, Leslie acts like his usual self and goes a little overboard.

Eddie and Melissa's relationship continues to progress but Philip has a secret that could change everything. Eddie has to deal with a difficult situation.

Richard and Sophie Hawkes attempt to build an eco friendly style house in Kent.