A study of WWII begins with a look at ethnic, economic and social issues that may have led to the start of the war. Harvard historian Niall Ferguson hosts.

The seventh season begins with the film "Heart of Darfur," which examines social and political unrest in Sudan, including the challenges faced by people at the Abu Shouk refugee camp in Al Fasher.

Season 2 ends with visits to Jackson Lake Lodge in Wyoming, Rocky Mountain National Park in Colorado, and Camp Denali and Glacier Bay Lodge in Alaska.

The qualities of strong leaders are discussed.

Jimmy Smits hosts a celebration of America's 232nd birthday. The 2008 party features fireworks, Huey Lewis and the News, Jerry Lee Lewis, Taylor Hicks, Broadway's Brian Stokes Mitchell, classical singer Hayley Westenra and soprano Harolyn Blackwell.

When one of the lodge's projects falls through, Red (Steve Smith) and the boys are stuck with truckloads of cement. Also: Red turns a boat into a hovercraft; Bill (Rick Green) builds a cement table. Harold: Patrick McKenna.

In "Inspector Lewis: Expiation," Lewis probes the apparent suicide of an Oxford housewife (Emma Croft). Hugh Mallory: James Wilby. David Hayward: Vincent Regan. Louise Hayward: Lucy Robinson.