A giant blue hand burst through the roof of the castle and grabbed Finn and Princess Bubblegum.

Finn and the princess yelled as they were abducted and whisked away from the safety of the castle.

‘Finn, the human, you have broken a royal promise, for which the penalty is trial by fire!’ the giant Gumball Guardian yelled as he held Finn and the princess in front of his round, blue face, which was half filled with gumballs. The second giant Gumball Guardian breathed fire.

Finn answered, not impressed by the enormous size of the creatures or by the fact that they could breathe fire.

‘Wait!’ Princess Bubblegum intervened. ‘He’s my friend! Isn’t there another option?’

‘Yes,’ the first Gumball Guardian replied. ‘Because you care for the promise breaker, we will give him a less hot trial.You must now answer…’

‘…maths questions,’ the second Gumball Guardian continued.

‘Mathematical!’ Finn cheered.

‘Finn, you’re terrible at maths!’ Princess Bubblegum reminded him.

Finn remembered, losing his enthusiasm for this challenge.

‘Now solve this,’ the first Gumball Guardian ordered as the other Gumball Guardian projected a complicated maths problem into the space in front of them. Finn choked. The multiple-operation problem – a mix of geometry and algebra and really big numbers – would have stymied even the most capable mathematician.

It was immediately apparent that Finn would not be able to answer. The guardians noted Princess Bubblegum’s pained expression. They did not like seeing her sadness.

‘Wait, I thought of a better one,’ the second Gumball Guardian said before Finn had to admit that there would be no way he’d ever get the right answer – or any answer – to the original problem.The first algorithm disappeared. It was replaced by a brand new one. This one looked more manageable.

‘Yes, yes!’ the projecting Gumball Guardian cheered. This was much better. ‘What is two plus two?’

‘Solve it – or die!’ the first Gumball Guardian threatened.

Princess Bubblegum looked at Finn sceptically. Even Finn couldn’t screw this up, right?

‘Um, four, right?’ Finn answered uncertainly. Was this a trick question?

‘Oh, correct,’ the Gumball Guardian admitted sadly. The Gumball Guardians started to shake.

‘What’s happening, Princess?’ Finn asked.

‘You defeated the broken royal promise,’ Princess Bubblegum answered.‘The Gumball Guardians are resetting.’

Finn and Princess Bubblegum screamed as the giants dropped them back into the castle.

‘Slam-a-cow!’ Finn cheered when they found themselves back in the princess’s lab. ‘That was tops. Who’s not good at maths? I was all like…four!’

‘Four, four, four,’ Princess Bubblegum repeated. ‘That’s it! The answer was so simple; I was too smart to see it!’

‘You’re welcome!’ Finn answered smugly.

‘Four is the last figure I needed to perfect my decorpsinator serum,’ Princess Bubblegum explained as she walked over to the chalkboard to fill in the missing number.

The serum was finally ready. Princess Bubblegum went through the castle and poured the liquid on the dead zombies.

Finn yelled in excitement as the half-dead creatures returned to life.

‘This is messed up,’ Jake said as he watched the zombies reunite with their relatives and friends, ‘but sweet.’

‘Man, you broke a royal promise?’

Jake asked Finn in amazement when the experiment with the zombies concluded. ‘You’re nuts. All you had to say was that it was a royal secret. I know what’s up.’

‘I hope you grasp the full consequences of breaking promises,’ Princess Bubblegum said to Finn.

‘Heck, yeah!’ Finn assured her. ‘If I break a royal promise, I get to fight zombies, throw slumber parties, awaken Gumball Guardians, and…reverse death itself!’

Princess Bubblegum chuckled, before turning grimly serious. ‘But keep your promises, okay?’

‘I promise,’ he said.