Remorse

This is the 34th Situation of Polti. Elements:

• a Culprit; 
• a Victim OR the Sin; 
• an Interrogator

Plot: The Culprit wrongs the Victim or commits the Sin, and is at odds with the Interrogator who seeks to understand the situation.
This is a difficult story to bring about in a RPG. The PCs are not going to be Interrogator - it would be then an Enigma story - or the Victim - they will become the Interrogator to make something about it - so they can only be the Culprit.
The story’s force is that the Culprit feels fear about being discovered and there is a real danger of the Interrogator doing just that.

Culprit

In stories, often the Culprit feels remorse, but it is not needed. Sometimes it tries to hide the remorse and forget, but the Interrogator Element prevents that. The conflict is usually between what the Culprit needs to do to stay undiscovered, the fear of the consequences of being discovered and even the remorse it may feel, making it think it’s more dignified to surrender than to be discovered.

PCs as Culprit

You can’t plan to make the PCs feel remorse, but they can feel it by themselves - for instance, being the Mistaken One in a Erroneous Judgement, and then learn about the mistake, they could feel guilty about what they did to the victim.
What you can plan is for one of their kin to be the Culprit and share its feelings with them. In that case, though, it is more a Discovery of the Dishonour of a Loved One. Also, if they are guilty of something but don't care about the damage caused, the appearance of an Interrogator and the risk of being discovered and punished may provoke this story

Victim

If there is a Victim, PCs should not be it. If they are the Victim usually they want to do something about it and then they are also the Interrogator, being the Interrogator role what carries their weight.

Interrogator

Should the PCs were the Interrogator then this is not about Remorse or the fear to be discovered, but an Enigma.

Development

The Culprit may conspire against the Interrogator or its investigation (Conspiracy), ask it for mercy or silence (Supplication), or do Daring Enterprises or Obtaining to eliminate evidences it may find

If the Interrogator discovers them, the story probably develops into Pursuit, Vengeance or Falling Prey to Cruelty/Misfortune. Remember the Interrogator needs not to denounce the Culprit, but it may blackmail it.