Nothing is ever simple in the Gibbs family, is it? Nor is grief and anger. In this case, Gibbs is thrown back in time when his mother-in-law from his first marriage is a witness in a murder case, who still blames him for "not being there" and "doing nothing". Things get even more complicated when it turns out the murder victim had ties to a Mexican drug cartel, the same cartel that was connected to the man who had murdered Shannon and Kelly.
Then things get even more messier when Gibbs realizes Joann had a hand in the murder and, technically he has to arrest her. Oh, wait, according to Ms. Hart (whom Gibbs retained as Joann's lawyer, funny enough), it was an illegal arrest and thus the case would fall apart in court. So Ms. Hart wins.... or does she?
Overall, a good episode and an interesting insight in to Gibbs past.