Joseph Smith married Emma Hale on January 18, 1827.
On the night of March 24, 1832 Joseph was dragged from bed by an angry mob. They stripped, scratched and beat him and then smeared his bleeding body with tar. They then ripped open a pillow and plastered him with feathers. They attempted to choke him and to pour poison down his throat.
Many Mormons will have heard this much of the story and ascribed the mobs anger to religious differences (as well as economic factors) . There may be more to the story.
It is written that Eli Johnson demanded that Joseph be castrated. (The evidence for the existence of an Eli Johnson is tentative. Brodie referenced a late source for this. However there are other sources that describe the motivation of the mob, I have posted about them here.) "Dr Dennison had been employed to perform a surgical operation, but he declined when the time came to operate" (Journal of Discourses, Vol. XI pp.3-4).
Eli Johnston (it would be more correct here to say the Johnson boys, John Johnson's sons) suspected Joseph of improper relations with his sister Nancy Marinda Johnson (or Marinda Nancy Johnson) who was 17 years old at the time.
Nancy became Joseph's plural wife in April 1942.
Nancy bore two sons whilst in Nauvoo. It is possible that Joseph Smith was their father.
(I read about these things in Fawn M. Brodie's 'No Man Knows My History: The Life of Joseph Smith'. See pp. 119, 462-464. You can find her sources therein.)