The Doctor had intended to take Alice to Rokhandi, the most perfect planet in the universe, unspoiled and pristine. What he finds there instead is an amusement park. He's a bit perturbed, but Alice convinces him not to take it out on the poor guy wearing the foam costume.

What the pair of them don't see is a young man being caught vandalizing a park wall with graffiti. Rather than seeming angry, however, the park security apparently want to reward the miscreant. They even offer him free floss. Unfortunately, the floss is actually a tube that attaches itself to the vandal's head and essentially brainwashes him. "Rokhandi is a friendly place."

Meanwhile, the Doctor is still sulking about what has become of one of his favorite places in the universe. He begins to accept that this is just the natural way of things. Nothing stays pristine forever. Eventually someone realizes the profitability of developing such a place. There's nothing he could really do to stop the natural progress of the planet, but he has noticed something rather unnatural going on. Everywhere he looks he see's only happy people. Happy, happy, happy, not an unhappy person in sight. It just isn't natural.

To try to stir things up, the Doctor intentionally begins shooting up a target shooting booth. It isn't long before the Doctor is approached by the youth who was vandalizing the place earlier. He is apparently now working for the park, and he offers the Doctor free Rokhandi floss. Instead, the Doctor prompts the happy employee to take him to someone who might have some answers. Alice follows the pair discretely, picking up a pellet gun along the way.

The Doctor is brought before entity responsible for the happy nature of everyone at the park. It is a great tentacled blob of a thing, a mental parasite that sucks the will, ambition and creativity of those who would like to make trouble. The park security team just want the Doctor to move a little closer so the parasite can make him happy too. Alice arrives just in time, and thanks to a pellet in the butt, the security team pauses in their attempts to placate the Doctor.

The reprieve is short lived. Before they can escape, their path is blocked by a less friendly group of security personnel led by a man who introduces himself as August Hart. Hart acts as if he knows the Doctor and Alice, and he doesn't appear at all fond of them. The Doctor and Alice, however, have no clue who the man is. They do know for sure that Hart wants to drag them closer to the mental parasite.

The Doctor learns a little more about the entity as Hart's men drag the pair of troublemakers closer to it. Offering something a person wants, gives the entity an opening into it victims' minds. Once in, it can suck all the interesting bits out. The Doctor suddenly decides to quit resisting, and a tentacle quickly reaches out to attach itself to his head. But the entity gets more than it expected. So much that it explodes.

With the entity's control gone, the employees and patrons of the park get their minds back under their own control, and they don't appear to be at all happy with August Hart. He makes his escape, cursing the Doctor for screwing up his little operation.

The Doctor and Alice emerge back out into the park and find things have returned to what theme parks should normally be, full of vomit and unhappy people. Order restored, such as it is, the pair can now continue on their way in the TARDIS.

Back at the corporate office, the CEO receives reports of the disaster at Rokhandi. It seems the Doctor has caused trouble for them before, and they aren't very happy about it. But worse than that, it appears the entity on Rokhandi was just a piece of a greater whole, and it's destruction has caused a reaction from the much larger entity.

Written by Al Ewing & Rob Williams  Art by Simon Fraser