"The Truth in the Lye" is episode five of season two of Bones, the forensic drama series based on the books by Kathy Reichs.
Booth is in bed with his ex (funny; she had a new boyfriend only a few episodes ago) and the mother of his son when he gets a call about a murder. He gets a second call, this one from Brennan, whilst he is in the bathroom and said ex answers it. Which provides moments of awkwardness - for Booth anyway - throughout the episode. Especially when Brennan starts talking about how intimate involvement is required by all mammals.
The Crime Scene
There is a body in a bathtub full of household chemicals on a construction site (lye is a pretty dangerous substance used as a cleaning agent - there's also the fact that it sounds like 'lie'). Said body is rather the worse for wear. The deceased male had a bone disease which is hereditary, so Booth and Brennan go and check up on a list of families in the area who have children suffering from the disease to see if any of them are missing a father.
Brennan finds one where the husband has been missing for several days. Then Booth says he's found the guy as well. Only it's the same man, Larry - just with two different families, neither of which knew about the other. Two wives, two children, two surnames and two totally different jobs supposedly. One of which involved working on the site.
Bigamy has a tendency to be illegal plus, if one wife did find out about the other, that's an immediate motive for murder. Brennan wants to tell the wives; Booth says that if they found out about the other, they could both want their husband dead and could have conspired together to kill him.
Two Suspects? Or Not?
Booth has had an interrogation room tricked out to be the 'visitor's lounge,' sends one wife into the lounge and then gets the other sent in as well to see if they knew each other. It appears they probably don't. Or they are really good actors. It seems that on the construction site he had taken a fairly large sum of money for materials but had cut corners on them and seemingly kept a chunk of the cash. Another motive, but it seems that might not be it either. Both wives still have a motive. When the wives are told about their husband, they do not take it well. Not a shock. Unless they are really good actors.
Things get really complicated before the murder is solved.