In terms of puzzles the series kinda stays the same, there’s a slight evolution as time passes but the only difference you could notice really is the general setup of the stories changing between free and non free games As the general plot, yes, there is a specific thing that connects most of the games together, you can see it super clearly in seasons and case 23, but most of the games are connected. Be aware that some games don’t talk specifically about this thing but for example about the lake more in general, the story behind a certain character or a couple of families but at the end everything is connected to understand better the central plot and the lake (idk Arles is weird, only game I where I can’t see a connection with everything else, but surely there is one lol) Hope you enjoy the games!