STORY LINE (in english):
On Seibold street in Kiel, a young woman is found dead in her apartment near a warehouse.  She was attacked from behind two to three days earlier..  The new tenant and the property manager discovered her there when the new tenant wanted to take over the apartment. The dead woman's name' was Renate Plikat.  'Police commissioner Finke finds out that she rented the place a year ago and her stepfather had reported her missing shortly before then.  Right before her death, she had withdrawn DM 20,000 from the bank.  Only' a 'notebook of her's was found containing 'contact details for clients and a call girl advertisement from a newspaper. 

Mr. Miesbach, who has his kiosk across the street from Renate's apartment, confirms that men often went in and out of Plikat's apartment.   Inspector Fink's lady police assistant named Ms. Scheffler appears pretending to be Plikat over the phone and she's accepting Plikat's phone calls and related appointments for Plikat that might indicate clues on what or who else is possibly involved.

Finke informs the girl's stepfather who seems dismayed and surprised about her second home that was that apartment, about which the stepfather says he 'knew nothing.  Nor, did' he say 'he knew anything about the 20,000 DM that disappeared from the apartment.  He claims that his stepdaughter worked as a saleswoman in a clothing store boutique and had no idea about her activities as a call girl.  The owner of the boutique stated that Renate Plikat was not only a salesperson there, but also a manager.  Her colleague testified that Renate intended to buy her own boutique in Hamburg.  In addition, a stranger called the boutique, he was waiting for Renate Plikat in a bar.  Finke's colleagues appear in the restaurant and find the man.  

Plikat also had a boyfriend her age, a secondary school student' named Bertram Schaarf 'who Finke also found.  He' says there was a 'meeting with Renate, where 'she wanted to break up with him.  Then, he 'says' went back to her to change her mind.  He' says he 'would never have been in her apartment' and that he only found out about her work from his mother after Renate's death.

While Finke's colleagues find Renate's other prostitution clients, Finke also questions the' stepfather of 'her ex-boyfriend, Mr. Schaarf.  He knew Renate from her visits to her house but like his wife, indicated that he was of the opinion that Renate was below the level of their son.  Commissioner Finke's assistants Franke and Scheffler find another prostitution client, but neither one of these clients nor the objects found in the apartment seem to reveal a trace.  Finke and Franke meet a man from the health department.  The prostitutes must be registered there.  Through an anonymous phone call, the health department came across Renate Plikat, who was not registered and they' indicated that she 'tried to disguise her activities.  Finke and Franke accompany the man to the red light district.  In a pub they find a newspaper clipping with Renate Plikat's advertisement.

Franke and another policeman look for' and find 'the pimp Heiko Schulz, who the police suspect because of the found advertisement that he wanted to become the pimp of Renate Plikat and' had 'contacted her.  He surprises and knocks Franke down and is able to flee in a sports car, but Franke and his partner catch up.  

Finke visits Mr. Schaarf, Bertram's stepfather because he suspects, based on a description of the person, that he was a client of Renate Plikat.  Schaarf admits to having been with her, but states that he asked her to stay with Bertram at least until he' finished secondary 'school, as he would have shown a total drop in performance' in his school 'work.  Finke asks about Bertram, but he is not at home.  Finke has found out that Bertram made false statements about his whereabouts on the day of Plikat's death, even though he had an' acceptable 'alibi.  

Meanwhile, several police catch Schulz.  When Finke leaves Schaarf Hermes a friend of Schaarf, comes by.  Finke returns to the presidium, where' Schulz is questioned on why he 'paid for his sports car with 20 DM 1,000 bills. Could it be Renate Plikat's?  

While across the street informally looking at suspects, Finke is hidden with kiosk operator Miesbach' and they are able to identify 'Bertram Schaarf.  Miesbach says that 'Bertram has often visited Plikat, so he lied on this' point, too.  Miesbach said that Bertram had often approached Plikat and harassed her.  Miesbach said that he also recognized Schulz' and that he was with her more often' and 'that Schulz was even with her on the Friday she was murdered, yet before that, she had' even 'left the house with still another man.  Possibly Bertram's stepfather, Mr. Schaarf?

Finke asks Bertram why he lied to him, but nothing can be got out of this.  Schulz denies that he wanted to do business with Renate Plikat, he just wanted to urge her to register.  He also denies having stolen her money.  
Later,  kiosk operator Miesbach calls the police about a newspaper article about the murdered woman's stepfather.  He is astonished that the stepfather was "shocked" by the double life of his stepdaughter, because he drove to the apartment several times.  The stepfather' of Renate Plikat says he is able to however prove 'that he was there for work because of his print shop' and 'to deliver print products next door.  Renate Plikat's stepfather actually' says that he 'can credibly assure them that this was just a coincidence and that ... "Plikat's stepfather did not know that his (own) stepdaughter lived' there" ... nor knew of 'what work she was doing there.

Police assistant Franke is able to confirm that Heiko Schulz confessed to the break-in and theft of the money, but he continues to deny the murder.  Finke found out that the water was turned off from three thirty to half past three due to a pipe burst due to night frost.  The corpse had been found in the apartment with the water running, from which Finke concludes that she left the tap open so that she would know when the water would be available again and she could make coffee.  But, she didn't make any coffee.  She should have stayed in the apartment for an hour and a half before she left the house at six o'clock without turning the tap back on.  

After seeing inspector Lutz,  Finke takes another look at Renate Pikat's locker in the clothing store boutique where she worked.  He finds out that Pikat's colleague Monika lied to him and showed him the wrong locker - her own - and not Renate's when asked to.  Monika denied having ever been to Renate Pikat's apartment, yet the kiosk owner confirmed that she could have been the girl who left the apartment at six o'clock, but he could not clearly identify Renate Pikat due to the darkness outside.  Monika bursts into tears and reports that Renate allowed her to use the apartment whenever Renate wasn't there.  She was even in the apartment with her friend Horst on Friday and they actually found the body there, but stayed quiet about it.  They fled the apartment and were so afraid, they did not' tell 'the police, because their parents would find out about her and her boyfriend sneaking around.

Heiko Schulz admits that he broke into the apartment at half past six.  The radio was on and the tap water was running.  It is therefore certain that she was murdered when the tap was not running, i.e. before half past four.

Bertram's mother tells Bertram that his father was with Renate that day to change her mind.  Maybe, Mrs. Schaarf couldn't possibly imagine that Bertram already knew that and even more.  Bertram immediately runs out of the place and out into the forest, disturbed because maybe he thought more had happened between those two.  Maybe, he even suspected this long before.  Mr. Schaarf tells his wife that his friend Hermes told him about Plikat's work as a prostitute.  He then sent his son Bertram to Plikat with 100 DM so that he could see that there was no point in shedding tears for a prostitute, yet the stepfather didn't know the full history of Bertram and Plikat's relationship.  Ms. Schaarf is shocked at hearing this.  

Finke turns up at the Schaarfs' household looking for Bertram.  The police then surround the forest.  Bertram holed up in the forest and his mother is there.  She tries to get him to give up on the loudspeaker, as did his father.  The situation remains tense until the next morning.  Then, the police go further into the forest.  Bertram, up in a tree has a rifle and opens fire on his father, but luckily he doesn't hurt anyone.  Bertram then shouts something about his stepfather having been there, but that Renate Plikat didn't want to sleep with him, even for the money.  Shortly afterwards he falls down from the tree, but survives seriously injured' and is carried away on a stretcher.'

SOURCE: (updated)
from Wikipedia Germany, Wikipedia the free encyclopedia
-- https://de.zxc.wiki/wiki/Tatort_(Fernsehreihe)#Liste_der_Tatort-Folgen
(see: 'Main article : List of crime scene episodes')