It's a direct continuation to Koodbool, but way closer to the original Duke 3D base level format with a layout-centric theme, falling under the Old Limits and with a non-Euclidian progression inspired by Lunatic Fringe.
A city block at night. Local amenities include a swimming pool, apartments, a grocery store, a sewer system and more. Duke wakes up in his hotel room, finds out that the city is under attack.
Yet another city at night - except this particular one is under a pretty fucking serious type of attack. You wake up to an alien ship having just crashed right down your apartment building.
Command noticed an anomaly in their Slipgate network. After sending a few scouting parties into the anomaly, none of which have returned, they are starting to fear the worst. They sent you in to investigate the anomaly and report your findings upon your return.
This time Duke is sent to some sort of a submarine base. The alien vermin has taken over a fortress by the sub base and it's your job to cleanse 'em out.