.. Cryptex four symbols

Follow the glow. Or multiple glow places around the house and outside.
Each glow will give you one symbol.

• In the bookcase at the office room
• Backyard, in front of the dog
• Glowing poster in Zoe's room
• Glowing mirror in the bathroom

After you know all the symbols (look at the cryptex to know how many you got) set the symbols correct.

Read the letter...

You need to burn the coal lump you found in the cryptex.