I'm hooked too; it's my Melrose Place replacement! I think Zack killed whoever's body is in the trunk and his Dad knows about it which is why he tried to hide the trunk. I think Mike the plumber is an undercover CIA or FBI person who's onto the fact that something is very amiss on Wisteria Lane, although that meeting with his "boss" looked like some sort of Mafia undergound connection.

Who do you think wrote the note to Mary Alice?