What major revelation did Anderson’s mother unveil before her death?

Having touched upon the subject of her father’s long absence several times before in other poems, Anderson takes the opportunity in the poem “ordinary damages” to tell the reader what her mother had told her before her death. Anderson’s mother had finally revealed that during his long absence from the family home, Anderson’s father had not been having an affair as Anderson had briefly suspected. Instead, he was committed to a mental institution at that time. He had also been diagnosed as a “manic depressive” (282) during his time studying to be a preacher.