What episode of Little House on the Prairie explains Mr. Edwards not being with his wife Grace and kids?

I know I've seen it, but I can't remember why he left.

Now it's gonna bug me.

Thanks alot ;)

OK found out what episode from season 8:

162. A Promise To Keep 03/01/82

Mr. Edwards begins drinking again because he can't forget the death of his son. His wife finally asks him to leave. Mr. Edwards returns to Walnut Grove. Laura and Almanzo decide to have Mr. Edwards become the godfather of their child. Meanwhile, Albert is trying to earn enough money to buy a microscope for a school project. Charles allows Albert to go along with Mr. Edwards to Sleepy Eye to pick up some goods. In Sleepy Eye, Mr. Edwards gets drunk. Mr. Edwards speeds out of the town with the wagon causing Albert to fall off it. Albert gets seriously injured when he is run over by another horse and wagon. Charles is furious at Isaiah and never wants to see him again. Laura steps in to help Mr. Edwards get over his drinking problem. Mr. Edwards gets better until he finds out that his wife wants to divorce him. He goes into Walnut Grove to get some alcohol, but when he sees the church, he changes his mind. Mr. Edwards then goes into the church to pray for the strength to get through this rough period.