Before the Nazi “Final Solution”, there were between three and four million Jews in Poland. The most shattering blow came with the establishment of closed ghettos to which Jews from the entire country were driven. Klezcew, however, was a small community in which the Nazis found that on-the-spot extermination of Jews was more practical.
The entire Jewish population of Kleczew was liquidated. They were locked up in a nearby ghetto (Zagorow) and then allowed to return to Kleczew to retrieve any family gold; then forced to dig their own grave in the Kazimierz forest. When completed, they were driven there by truck and forced to jump into the pits. Then, without firing a shot, lime was then poured onto them, effectively burning them alive. Looking for memorials a researcher writes,

There, walking in a small path, we reach a Polish shining memorial, with a huge cross of Jesus Christ and Polish wordings, engraved in gold. There are also flowers on the ground. The plaque commemorates the victims of WW2. No mention of the Jews.  
Then they lead us into the forest itself. We cross branches and leaves and bushes and get to a much smaller memorial, surrounded by white pillars. The memorial says in Polish that here is a memorial for the Jews murdered by the Hitlerians in 1941-1944. It stands on a mass grave.
We pave our way further deep into the forest, and there is another monument, with the same text. We return silently to the car . . . there are about 4-5 more such memorials inside the forest.
I would have never guessed, not to speak of a stranger passing by, or a local Pole, coming there often to play or watch the football games.

  The cemetery was razed and is now a soccer field.  In destroying it, the Nazis used the headstones for paving (several are now preserved in the museum in Konin.) They even dug up the bones, placed them in a mass grave, and built a public lavatory over it.

They probably would have destroyed the synagogue, too, built in the middle of the 19th century. Its size, though, made it useful as an auditorium. At least the Zekinds (Aarons’) had left for the New World before these tragedies occurred.  More on Kleczew can be found on the internet at the following sites: 

The only mention I recall in our family, were some discussions about sending food and clothing to relatives still in Poland, most probably Gusta’s relatives who did not emigrate. I recall considerations along this line between Samuel and Tobias, the children of Lehman and Gusta. I don’t know if this was done, and perhaps this was a general attempt to aid the extant Jewish population. After the war, of course, there were no Jews left in Kleczew.