Not a very original story but it's atmospheric enough to work with the bet in the background. The bet itself is very funny, with the entire station in on it. The opening scene is hilarious.
There is never any doubt that Alexis is Castle's daughter – there's nothing of her mother in her at all! Solving the mystery of her boyfriend's 'chance' meeting with an old 'friend' – she spends way too much time with her father!
The 'Strangers on a Train' idea is a good one but it never works – it relies completely on trusting a stranger and one of them is bound to crack. Not to mention trusting that the other person will actually follow through. Theoretically, if both didn't talk then the cases would be almost impossible to convict without non-circumstantial evidence. In this case, the only thing that tipped the cops off that the cases were connected was the related water content and there's no way the killers could have predicted that.
A funny episode and though not a very creative solution, it's still an interesting case.