The excellent and thoughtful series “American Experience” (8 p.m., PBS) returns for a new season with “Two Days in October,” a harrowing look at the Vietnam experience. Presented as two parallel stories, “Two Days” recalls a tragic military debacle and an early student protest that spiraled into unexpected violence. Participants, now well into middle age, remember how each event changed them forever.

The first story concerns the Black Lions, a special Army unit under the command of Lt. Col. Terry Allen. Allen, the son of a decorated World War II general, was under pressure from Army brass to search and destroy Vietcong troops. He was also reeling from his wife’s decision to divorce him – a decision, we learn, that stemmed in part from his young wife’s disenchantment with the Vietnam War.

Back home in Madison, Wis., some students decided to stage a sit-in to prevent Dow Chemical, then known for its manufacture of deadly napalm, from recruiting students on campus. While some students were inspired by antiwar sentiment, the vast majority remained completely oblivious to the protest, and possibly to the war itself.

“Two Days” also hears from the sister of a soldier killed with Lt. Allen, several professors on different sides of the Wisconsin riots and two Madison policemen with no qualms about their actions.

¢ Having sent up nightly news with “The Daily Show” (10 p.m., Comedy Central), Stephen Colbert now parodies pompous punditry with “The Colbert Report” (10:30 p.m., Comedy Central).

Tonight’s other highlights

¢ A local deli names a sandwich after Deacon, making Doug jealous on “The King of Queens” (7 p.m., CBS).

¢ St. Louis and Houston tangle in Game 5 of the National League Championship Series (7 p.m., Fox).

¢ Ed gets a prescription for relaxation on “Las Vegas” (8 p.m., NBC).

¢ A pool boy skims his last drowned fly on “CSI: Miami” (9 p.m., CBS).