He appears only after you have watched all of the videos in the room (you don't have to watch them all the way through).
When you come downstairs in the Mews mansion, and enter the museum at the right, your character will suggest watching the 5 videos on the cryptids. So you have to do that before Mews will appear again.
You awake in the Mews mansion. After he leaves, drink the water, go downstairs, and enter the museum (first floor right). Review all 5 of the cryptids videos and then Mews will join you.
The Cryptids Museum is on the first floor of the Mews mansion, to the right.
Review the 5 videos in the museum, and Mews will appear to give you further instructions.
When you first enter the museum in the Mews mansion, you must study the 5 cryptids that are displayed there. (You actually only have to start and stop the videos.) When you have done all five, Mews will appear and talk to you about the quest.
In the museum, first floor right in the Mews mansion.
The Cryptids Museum is inside the Mews mansion (first floor, right). You will review the videos there and bring evidence to the lab.
When you come downstairs in the mansion, go to the right and enter the museum. You are supposed to watch all five cryptids videos (or just open and close them), and then he'll come in to give you some instructions.
Go downstairs and to the right, to the Cryptids Museum in the mansion. Look at the 5 videos of cryptids, and Mews will return to give you some instructions.
After Mews leaves your room, drink the water and go downstairs, to the museum on the first floor (right). Watch the 5 videos and then Mews will arrive and you can begin hunting for the cryptids in his helicopter.
You have to look at the 5 videos in the museum and then Mews will show up. (You only have to open each one, not look at the whole thing.)
When you come downstairs in the Mews mansion, go to the museum (first floor right) and view all 5 videos about cryptids. Then Mews will appear to give you instructions.