In One Night: Full Circle, there are two wildly different endings you can be presented with at the game's close depending on how you played during your adventure.

One Night: Full Circle determines which ending you will recieve by tracking your score on a morality scale. At the end, the score you recieve will determine your ending. This score is used in the background by the game and there is no way for you to check it in game.

You can perform various actions to change your score on the internal morality scale. In cutscenes, the responses you pick to other characters' prompts will either raise or lower your score, depending on the nature of the response you pick. Also, defeating random non boss enemies (which you can avoid without resorting to combat) will lower your score.

Note: This said, it doesn't mean you shouldn't defeat enemies. You can still defeat somewhere between five and seven enemies in the game provided that you are also raising your morality through certain choices in cutscenes. Even if you don't you can still kill two or three before your morality falls low enough as to give you the low morality ending.