Free, text-based game, and yet one of the best mystery games I've ever played. And it's my favorite genre, and I played a LOT of them, from my childhood up to today, from old-fashioned point & click games up to modern detective games like Obra Dinn, Golden Idol or TR-49
And yet this one managed to crawl itself in my memory. Now whenever someone asks for a recommendation, I always include this one in my "must-play" list. Well done!