The pups are watching Thunderbolt P.I. saving his partner Rex Hunter from the evil scientist, Dr. Wonko, before Spot turns off the television, thinking it was over. Whilst Rolly and Cadpig state that all the footage that was being shown was a preview of tomorrow's show, Lucky is upset since Thunderbolt is the only excitement he can find on the farm.
Suddenly, via the barking chain, Kelly the Sheepdog reports on how a lamb has strayed from the flock and was last seen heading for Gruteley. The Bark Brigade are asked to find and return the lamb. Lucky isn't impressed by this and wonders which poor suckers will be stuck with that assignment...cut to the pups and Lt. Pug outside Gruteley, having been assigned.
Lucky complains to Lt. Pug on how they don't get exciting assignments like Thunderbolt, to which Pug responds that this is real life, not a television show.
As the pups and Lt. Pug look around town, Rolly's nose leads them into an alley way; however, they find a dead end and realize it was a trap. A can of garbage is tossed at them, and Pug is trapped under a grocery cart.
The "lamb" turns out to be a large Goliath-type sheep called Lambo and vows never to go back to the flock. Lt. Pug flies into a fit of rage and passes out as a result.
Whilst the Bark Brigade procedure is to turn tail and run, Lucky realizes that this is the excitement he has been longing for and sets off to trap Lambo.
Lucky figures Lambo will get hungry, so the pups ambush him at the Gruteley nursery. When they try to toss a net over him, Lambo easily bucks them off, and the pups are covered by a birdbath dish.
Lucky puts his second plan into work, where they lure Lambo into the toy store by playing "Mary Had a Little Lamb" on a music box. Annoyed by the incessant nursery rhyme music, Lambo runs into the store, and the pups lasso him on a rocket ride. However they get dragged through town, resulting in Cadpig, Rolly and Spot falling into some fertilizer and Lambo taking Lucky hostage.
At Lambo's hideout, Lucky is tied up with duct tape, before Cadpig arrives to act as a negotiator for Lucky's release. However, Lambo refuses to negotiate and dares Cadpig to talk herself blue in the face, to which Cadpig happily complies.
Lambo, however, finally surrenders after being driving mad by the many hours of Cadpig trying some psycho analysis on him.
Cadpig is commended for her bravery and cleverness, and Lucky has had most of his fur pulled off from the duct tape, but he is still named a hero for helping catch Lambo. However, Lucky, considering what happened, doubts his hero status.
- Dr. Wonko in "On the Lamb" has a bit of a similar design to Gene Wilder's incarnation of Willy Wonka (the name Wonko is probably a reference to Wonka as well).
- Rex Hunter's design and character pays homage to James Bond, especially with the Martini and being strapped to a table with a laser aimed at him.
- When Lucky states, "Boldly going where no puppy has gone before," his dialogue is most likely an allusion to the Star Trek slogan: "To boldly go where no one has gone before."
- Kelly the Sheepdog with control issues could most likely be the same Kelly from "Tic Track Toe", whom admitted in Cadpig's group therapy to being scared of sheep.
- Lambo's appearance and name is a homage to Sylvester Stallone's portrayal of Rambo.
- "Luckybolt" was also heard in "The Life You Save".
- In the Gruteley nursery, one of the hedge trimmings is in the shape of a Hidden Mickey head.
- In one shot, Lambo is walking by the "Hobby Lobby" and "Book Store"; however, in the next shot, he is walking by "Cruella Cares" and "Devil Toys", which is actually south to where the former two stores are.
- "Cruella Cares" and "Devil Toys" was the store Roger donates his old teddy bears to in "You Say It's Your Birthday".
- Cadpig, Rolly and Spot falling into the fertilizer may be an homage to the running Biff Tannen gag in the Back to the Future trilogy.
- Spot almost utters the "S"-word when she says, while in the fertilizer, "And I thought we were in deep...er…trouble."
- Amongst Lambo's loot is a teddy bear, baseball bat, hockey stick, toy helicopter, bucket, basketball, wind-up kitty, toy jeep and banana skin.