Viewers voted online and selected the four couples competing in challenges, which involve a muddy search for objects, a junkyard encounter with attack dogs, and an airborne bus. Also: a "home invasion" stunt in Portland, Ore.

The episode starts out with the four remaining comics on stage to find out who received the least amount of votes from last week's America vote. The three remaining comedians then have five minutes each and America votes to decide who will remain in competition to be the "Last Comic Standing".

The nominated houseguests (Mike "Boogie" and Erika), as well as the HOH and two other houseguests compete for the Golden Power of Veto. The houseguests also compete in the first luxury challenge of the season, and the veto ceremony shakes things up in the house.

Jack Carter accidentally shoots Henry while suffering from short-term memory loss. A visit from a noted scientist may hold clues into Carter's sudden memory loss.

Cesar reflects on some of his most difficult cases and shows how his LA dog psychology center ("the home of his pack") has helped in the rehabilitation process. He also introduces some of the dogs, including a few owned by celebrities.

The crew faces more than accustomed when rescuing a man from his burning apartment; Sean has a request for Maggie's dad; Franco thinks his new girlfriend is hiding something from him; and Tommy realizes that his crew's future together may be in jeopardy.

Tyler plans to run a marathon, but wants only three roommates---Jose, Paula and Zach---to be there in person to cheer him on, which offends the others in the house.

TONIGHT: Professor of Middle East and South Asia politics and author of The Shia Revival: How Conflicts within Islam Will Shape the Future, Vali Nasr.

Tonight former editor for the New Republic and author of The Good Fight: Why Liberals--And Only Liberals--Can Win the War On Terror and Make America Great Again, Peter Beinart.