By mid-December the light is gone from Algonquin before five o'clock, and the cold arrives the moment it goes. Sundown Enterprises, Inc. runs snow removal into that dark, plowing driveways and lots, cutting the walks open, spreading salt on the slopes and shaded north sides that lock up first once the sun quits. Evening snow is its own particular problem, falling on warm pavement, melting, then setting solid by nine. Clearing it before that happens is the difference between a driveway and a skating rink. Somebody has to be out there while everyone else is home with the porch light on, and that is the arrangement.