The truths and half-truths about Dr. Venture's past arch nemesis, Dr. Girlfriend and The Monarch, are revealed.

Dr. Venture learns that a life without an arch enemy is not fulfilling.

Billy Quizboy recovers the memories of his former life as a failed TV Quizboy, the loss of his hand and eye in a dogfight, his recruitment into the OSI, and his first mission as a spy.

With the Monarch busy settling into his new home with his wife, a new villain arises to arch Dr. Venture.

Dr. Venture decides to raise money by running a Day Camp for Boy Adventurers. Things don't go quite as planned when a giant ape gets loose, Action Johnny loses it, Sgt. Hatred arrives for an unscheduled bush burning, Hank gets a new friend who pushes Brock's buttons, and the Monarch sends the Moppets in to spy.

Team Venture meets Team Quymn, led by Dr. Tara Quymn, Dr. Venture's childhood sweetheart. Her two twin daughters and manly bodyguard seem oddly familiar, but the two teams must join forces to battle a dreaded were-o-dile: half man, half crocodile.

Brock and Dr. Venture stumble into a hidden state-of-the-art fallout shelter beneath the Venture compound, while Hank and Dean call in Dr. Orpheus to summon the Order of the Triad and help them out.

The Monarch gets word that Dr. Venture and Brock are at a science conference, and decides to launch an attack on the Venture compound.

Dr. Jonas Venture Jr. builds a museum in honor of his "father," and invites all of Jonas Sr.'s old friends and enemies to the grand opening.

The Monarch leads an attack on his new arch-nemesis, Dr. Jonas Venture Jr., at his base on Spider Skull Island.

Billy Quizboy has spent thirty years trying to decipher a series of cryptic clues hidden in Rusty Venture Cartoon Show episodes. Finally the solution to the mystery is at hand, but the answer forces Brock to discover what his true orders are.

The OSI has put a termination contract on Brock's head, and three top assassins plan to collect. Meanwhile, the Monarch and Sgt. Hatred battle to see who will be Dr. Venture's arch.

Heads will fly as the explosive conclusion of The Venture Bros. two-part season finale finds Brock and the Venture family on the run from the Law, The Monarch, Sgt. Hatred and the entire O.S.I!