If I take the mascot up the stairs I get caught

Hint 1 of 4:

You can't escape up the stairs. Look for another exit.

Hint 2 of 4:

Why do you think the Sewer map was included with the game ?

Hint 3 of 4:

CAST FRIMP ON COVER to go down to the sewer.

Hint 4 of 4:

You need a lightning bug to see down there.