HOW DO I OPEN THE LOCKBOX?

Remember that pen Mahrute gave you?

Calvin must have been busy leaving clues in the cab. Have you explored the cab lately?

Look at the graffiti behind the driver's seat. You'll need to shed more light on it.

Use your penlight on the graffiti, and tap at different places to move the light to where you need it.

One particular message seems to have been tampered with.

Some of the letters do resemble numbers if you squint, don't they?

HENRY SN1TCHE5 TO T4E FU2Z

The code is 1542