In 1992, the couple's marriage fell apart in devastating fashion, with an affair and horrifying allegations of abuse. According to a 1992 Vanity Fair article, Farrow repeatedy discovered Allen acting strangely around their daughter Dylan, and it allegedly escalated into outright abuse (warning: the link above contains occasionally graphic descriptions of Allen's alleged abuses). The resulting custody battle became the stuff of media headlines, with Allen accusing Farrow of coaching Dylan and Farrow laying out the graphic abuses he had apparently committed.
The battle was made worse by the fact that, months earlier, Farrow discovered that Allen had been having an affair with her adopted daughter, Soon-Yi Previn, when she found a stack of nude photos Allen had taken of Previn. He later married Previn in 1997.