Before the war, Marianna and Jan lived in the village of Miszew. There, they met the Jewish Kasman family – Markus and his wife. Marianna and her mother were both maids in the Kasman household; later, the Jewish family also hired Jan as a physical worker. Marianna and Jan had four children: two daughters, Urena (born 1924) and Janina (born 1929), and two sons, Michał (born 1932) and Mirosław (born 1934). During the occupation, both families lived in Warsaw.
After a ghetto was established in Warsaw in the autumn of 1940, all Jews, including the Kosman family, were forced to move there. However, the family managed to survive the large-scale liquidation operation carried out in the summer of 1942. Some time later, on 24 September, they fled from the ghetto. For two days, they hid in their friends' house, but they had to leave due to security reasons. At the time they owned the so-called “Aryan” birth certificates. Markus Kasman's documents stated that his name was Michał Kalinowski – which was also the name of Jan Krzysztoszek's cousin, who died in 1939.
The Kasmans asked the Krzysztoszek family for help and shelter. Seeing that they were their long-time acquaintances, the couple agreed to help them. Marianna picked Markus and his wife up from the Gocławek train station and, together with Jan, brought them to their flat in Powązki.
The Krzysztoszek family's flat was very small – it had a tiny room, a kitchen and a hall leading to a field. The entire operation took place on Sunday. They had to be extremely cautious so that their neighbours wouldn't notice anything.
The hiding place arranged for Markus was a chest in the hall, right next to the roof. At first, the Kosner couple lived together at the Krzysztoszek household, but due to their financial struggles and high risk of being denounced, Kasman's wife had to move to a hiding place in a flat located on Nowy Zjazd Street.
The Krzysztoszek family was not a wealthy one, so Kasman felt guilty for putting an additional load on them. But Marianna told him: “I know that you worry about not having any money. I assure you that we will always share soup with you and for me, it's a great honour to be able to extend my hand to you.”
From time to time, Markus left his hiding place to talk with Marianna and Jan. They also gave him newspapers to read. Irena helped with housework, cleaned up and made sure that nobody saw their illegal guest. Moreover, she served as a connection and carried information between the hiding places of the Kasmans and the two brothers of Mrs Kasman, who were hiding in an apartment on Miedziana Street.
On 21 July 1943, a manhunt took place on Czartoryskich Street 8 (currently Dolnośląska Street), but Marianna and Jan managed to hide Kasman behind the chest and he was not discovered. Before the outbreak of the Warsaw Uprising, Markus moved to the flat on Nowy Zjazd Street. From then on, he lived together with his wife and his brother-in-law. During the Uprising they left Warsaw and lived in various villages in the countryside, where they worked for local peasants. They survived the war.
After the end of WWII, the Kasman family lived in Łódź and later migrated to France. They kept in touch with Irena's parents until their death.
