St. Peter informs God that he's taking a vacation for 2 weeks. God has to appoint a temporary substitute. And so he goes to Lük's home in the outskirts and informs him he's been appointed temporary pearly gatekeeper, seeing as Lük doesn't have anything important to do at all. Lük doesn't find a way out of this, so he has no choice but to 'face the music'.
Lük is at the pearly gates letting recently-deceased people in. He lets in a 43-year-old mailman who was killed by a bunch of hounds. Next is a 87-year-old woman who died of stage 4 cervical cancer. After that, it's a 74-year-old rabbi who accidentally cut himself while performing a bris. Lük feels extra exhausted by this crap and drinks some whiskey. He then meets a heavily-clothed person who has his face covered. He says he died of only natural causes. Lük got suspicious, but was too drunk and lazy to find out about the mysterious person so he lets him in.
Lük meets another heavily-clothed person telling him he died of falling on his head on a floor filled with thumb tacks. He lets him in. Soon after, a family of heavily-clothed people arrive telling Lük they died of a car explosion inside the Grand Canyon. When the alcohol in Lük wears off, he is unaware he let in heavily-clothed people into heaven. He decides to leave the pearly gates and sees who those heavily-clothed people really are. He searches all over heaven for them. He ends up in an alleyway, and he spots some of the heavily-clothed people. They remove their clothes and Lük is shocked to discover that they are actually demons in disguise. Lük goes to God's mansion and tells the heaven elites that demons are sneaking into heaven.
God commands Archangel Grant and the Angelic Guard to capture all the demons and send them back to hell, but the demons retaliate by using guns and other weapons. Next thing you know, demons soon take over heaven. The heaven elites blame Lük for letting them into their holy land. Lük comes up with a plan to get rid of the ravaging demons, which involved a hot air balloon and Sal Coddington's fish.
Lük runs out all the demons who snuck in to heaven by leaving a trace of fish and telling them of free food. When they reach the pearly gates, the angelic guard captures all the demons, puts them in a cannon and sends them back down to hell.
St. Peter returns from his vacation and sees heaven wrecked by the demons, but he didn't care, and neither did Lük. God punishes Lük for letting in demons by making him clean up all of heaven "until the end of all time".