Reny is out of her room. You have to get inside Slug's, where Stefan went.
The front door is not the way in, but maybe from the back...
Unlike normal walkthroughs, in Nice Game Hints you can select just the puzzle you want hints for. Here are listed the puzzles for "Level 6 - Reny in the streets of Kapia" in Kapia. The guide you choose only contains information about that puzzle, reducing possible spoilers for other puzzles.