In the novel Lyddie by Katherine Paterson, what led to Lyddie's dismissal from the mills? In modern terms, what would we call Mr. Mardsen's...

Lyddie is dismissed for stopping Mr. Marsden from what today would be called sexual assault on Brigid.

Mr. Mardsen, the mill supervisor, is a predator.  He uses his position at the mill to take advantage of young girls like Brigid who either do not know what is going on or are afraid of saying anything for fear of losing their jobs.  Lyddie is very protective of Brigid, one of the young Irish girls she has...

Lyddie is dismissed for stopping Mr. Marsden from what today would be called sexual assault on Brigid.

Mr. Mardsen, the mill supervisor, is a predator.  He uses his position at the mill to take advantage of young girls like Brigid who either do not know what is going on or are afraid of saying anything for fear of losing their jobs.  Lyddie is very protective of Brigid, one of the young Irish girls she has trained.  One day she sees Mr. Marsden acting inappropriately toward her.

"Please‐no‐‐" She ran down the aisle between the looms toward the voice and saw in the shadows Brigid, eyes white with fear,and Mr. Marsden's back. His hands were clamped on Brigid's arms.

"Mr. Marsden!" (Ch. 20)

Lyddie sees Mr. Marsden trying to force himself on Brigid.  She stops him, acting without thinking.  She attacks him with the water bucket to stop what he is doing to Brigid.  Mr. Marsden gets his revenge by having Lyddie dismissed, ironically for acting immoral. He is the one who was being immoral.

 “[It] is not her work as such. Indeed," and here, he gave a sad little laugh, "I at one time thought of her as one of the best on the floor. But"‐he turned back to the agent, his voice solemn and quiet‐"I am forced, sir, to ask for her dismissal. It is a matter of moral turpitude." (Ch. 21)

When Lyddie looks up the meaning of "turpitude" and realizes that he is accusing her of acting immorally, she is upset.  She reacts by writing a letter to his wife and giving it to Brigid, while also warning Mr. Marsden to leave Brigid alone.  She tells Brigid to send the letter if she has any more trouble with him.

In modern times, we would call what Mr. Marsden did sexual assault.  It is not just illegal but also immoral for a man to force himself on a woman or even make unwanted advances (which is called sexual harassment).  Women have a right to have control over their bodies.  It is even worse when an employer behaves this way toward a woman in his charge.