Return to Plainlands is a drama/comedy about Erkki Hakala (Kari Väänänen), a tax evader who returns to Plainlands (on the west coast of Finland) from Florida to claim what is rightfully his: a place in the community and his wife, Kaisu (Mari Rantasila).

The tax fraud that initially drove Erkki away from home has become statute-barred, and Erkki has become a millionaire by selling cars in Florida. Erkki has his mind set on buying a medium-sized metal workshop, and sealing the deal is only short of the owners' signature. Erkki is even looking for a house of his own for the new life he intends to spend with Kaisu.

Erkki has decided to realise all his plans in the course of one day, on "the first day of the rest of his life". This is not an easy task. He has to settle the score with his family and convince Kaisu that he is someone easy to live with.

Erkki begins the rounds with his family at the graveyard, which is where it seems that his close family has the least ill to speak of him.

Erkki's living family in turn cause him a lot of trouble. His brother, Paavo complains about his various ailments and pines for Erkki's compassion. One of Paavo's sons, Raimo, has just brought under the hammer the carpet weaving mill Erkki had passed on to him, and Paavo's other son, Markku, suspects his wife of cheating on him. The whole entourage keeps following on Erkki's heels while he tries to organise his affairs.

In the city of Seinäjoki Erkki and the men of his family are joined by Erkki's crafty business partner, Taisto Matsomppi. When an old teacher on his last leg leaves the hospital bed and joins the crew, things finally start coming along.

Buying the factory becomes more complicated, since the Partanen with their plotting and scheming make both the buyers and bankers sweat. Occasionally they all embark on a good old American-style car chase on local country roads.

And yet all day long Kaisu keeps haunting on Erkki's mind. The whole village seems well up to date on their relationship. Meeting with Kaisu turns out the greatest challenge in Erkki's day, and not until the sun rises again is an understanding found.