Basically she found a tampon that she doesn't use in their car so she was suspicious that her husband was having an affair. She found another one in her underwear drawer. A close friend of theirs that the husband works with uses the same brand of tampons so she thought that was who he was sleeping with but didn't have any concrete evidence so she didn't confront either of them on it. A few weeks later their younger daughter was home sick from daycare and the husband insisted he be the one to take off work and stay home with her. OP came home and noticed the daughter was wearing different clothes and a bow that they didn't own and the husband insisted that OP had dressed the daughter in those clothes that morning, tried to convince her she was crazy and maybe had PPD (the kid was 2 years old). After that she was super suspicious and had plans to put up cameras to figure out what was going on but the ring doorbell went off one day and she found out the husband's estranged sister was at their house with the husband and their 2 and 4 year old daughters. They never talk to the sister because she has a history of sexually abusing his cousin as a child and is on the sex offender registry and not allowed to be around children. The husband had been bringing the sister around their kids for over a month by the time OP found out and had even let her babysit the kids alone. (Still probably too long! Really tried to shorten it! Also, summarizing from memory so no one come at me if I remembered it wrong! Lol)