We had to pause it and talk through it last night as it did escalate very quickly from 'here's Laura's laptop and phone's to 'let's look at this house' to 'we have a body'.
So the lady who was murdered at the start, Laura, had been googling the name of someone she went to school with before she died. Her phone's tracker showed she visited the last known address of the school friend before she was killed.
Said school friend's wife had gone missing two years prior and he had vacated the family home at that time. The police and Jack were suspicious because the wife was reported missing by a friend, not her husband. However, the investigation into her disappearance was dropped because a police officer said he had spoken to the missing woman.
Jack noticed blood in the kitchen so they dug up the patio and found a woman's body. I suspect the connection will be that a police officer may have covered up her murder by claiming to have spoken to her, when she was in fact dead. Whereas Laura's abusive ex boyfriend wasn't charged with his abuse as he was a police officer and was allowed to quietly leave his job instead.
Right at the end they see more of the material the missing wife's body was wrapped in and think there may be a second body. Then it cut to Frank, Laura's sperm donor, being severely beaten in an underpass. So we haven't seen yet if another body is under the patio or not.