History has taught us that when it comes to secret affairs on The Young and the Restless, they tend not to remain a secret for too long and they always cause chaos. Additionally, the affairs usually aren't just one-time occurrences.
Take for example the epic love triangle of Nick (Joshua Morrow), Sharon (Sharon Case) and Phyllis (Michelle Stafford). What started out as a "mistake" one night between Nick and Phyllis led to the pair having an ongoing affair and conceiving Summer, eventually destroying his marriage to Sharon. Phyllis and Nick would eventually repeat history by having an affair together years later while he was engaged to remarry Sharon; that marriage never came to be.
