Ducrau, an old sailor, rules over a small empire of boats and barges along the Seine. One day, he is wounded by an unknown man and pushed into the river. Maigret's investigation into the resistance of the so-called 'canal rats', as the people of the Seine call themselves, reveals a very bitter family tragedy. Did the constantly drunken gassin have a hand in this attempted murder? His daughter is said to have had a child by Duke's son Jean. But engineer Bebert could also be the father. Jean and Bebert are found dead... Based on the 18th Maigret novel L'ecluse n°1 (1933), published in German under the title Maigret in Nöten. It was originally published between 23.05.1933 and 16.06.1933 in the daily newspaper Paris-Soir as a serial novel in 25 parts.