Abstract: If you want to loose your way in a forest, just flip a coin at each crossroad and get the direction chosen by the coin. In other words, define a Markov chain in the forest. By using some tricks, I know that I can always go back to my steps. I will show how to do that. More generally, the plan is to describe properties and problems related to networks of interacting objects in which we define a perfectly reversible dynamics. The scenario involve mainly a quantum mechanical perspective, but I shall also try to consider information flow in agent-based models in economics.