You guys, seriously, this show is making some pretty interesting choices; it goes to show how much more conducive it is to writing a good story to have the end in sight. So:
LaGuerta stops by to see the old Captain and tells him her theory about the BHB; since he just so happens to own a boat, he's on her list of people to follow up with. Given how she cost him his job, he's understandably snippy at first, but later, he tracks her down and offers her information on the people on her list (of cops who own boats, essentially) if she'll help him get his pension reinstated. It's a classic pairing of people who don't remotely trust each other, with good reason, so it should be fun.
Two charred corpses lead MM (well, Dexter, really) to conclude there's a serial arsonist-murderer out there who's been wearing a protective suit so he can watch his victims burn alive. Could it be the random arson investigator who seems just the right amount of creepy to be a secret killer? Probably!
Dexter goes to Deb and tries to make her feel better about her confession, telling her that he understands since they've been the only constant in each other's lives. This does make Deb feel better, but meanwhile, Dexter's bond with Hannah is growing ever stronger. Also, in the wake of the failed attempt on his life last episode, Isaak Pullo gets a tip that the Brotherhood has sent two more assassins to take him out. These men are known to him to be the deadliest of the deadly, so Isaak Pullo, needing help from a source of whom the assassins are unaware (i.e., not Lurch), goes to the only other killer he knows – Dexter. He offers Dexter his life if he'll help him, and although Dexter initially refuses, the offer does intrigue him. He ends up being forced to accept, though, when Isaak Pullo, having had Lurch keep tabs on Dexter's movements, kidnaps Hannah to use as leverage to insure Dexter's help. Isaak Pullo promises that if Dexter goes along, he'll not only free Hannah but will drop his death mark against Dexter and will walk away from Miami forever.
While they're thrown together, Isaak Pullo, long fascinated by his nemesis, tries to get into Dexter's head, but Dexter's the one who wins their mind games as he realizes that Isaak Pullo secretly blames not Dexter but himself for Viktor's death; still, Isaak Pullo realizes that Dexter is having trouble facing his feelings for Hannah. Dexter ends one of the assassins before he ever knows what hit him; aware that this means Isaak Pullo is on to him, the second assassin goes to Jason Gedrick for help finding Isaak Pullo, and Jason Gedrick gets the bright idea to track down Dexter, with the idea that Isaak Pullo won't be able to stay away from him. Unfortunately for Team Brotherhood, the Dexter/Isaak Pullo alliance accurately anticipates this development and picks off the second assassin, but still, all doesn't quite go according to plan – more on that later.
Despite her assertion that she'll never approve of Dexter's relationship with Hannah, Deb helps Dexter where she can in his efforts to save her – and she's the one, once Dexter points her in the right direction, who tracks down the spot where Lurch is holding her. However, Hannah the secret killer is not one to let the grass grow under her chains, and manages to hoodwink and kill Lurch, but not without suffering a stab wound that would have turned out to be mortal – if Deb hadn't shown up to save her. In the hospital, Hannah points out that Deb could have let her die, but Deb tells her that that's not who she is – she's not like Hannah. I guess if she had to save her life, rubbing that sentiment in her face almost made it worth it.
So, getting back to the second assassin, Dexter and Isaak Pullo's trap works perfectly, and while Dexter mops up the guy's blood, Isaak Pullo heads off, intending to leave Miami and fulfill his promise. Unfortunately for him, Jason Gedrick has been having a really bad day -- annoyed that Quinn wasn't returning his calls, he banged Nadia (well, that part probably wasn't so bad), so Quinn beat the crap out of Jason Gedrick and took Nadia out of the club. Between that and the failure of the assassins, Jason Gedrick decides to put a bullet in Isaak Pullo himself, and although it's not immediately fatal, Isaak Pullo knows that the fact that the bullet is still in him means he's a dead man. His dying wish is to be buried at sea so he can be reunited with his love, so Dexter, kind of touchingly, makes that happen. Isaak Pullo's dying advice is for Dexter to go for it with Hannah; he was like Dexter before he met Viktor – detached and coldly logical – but with Viktor, he never had to hide who he was. So in the end, Dexter crawls into Hannah's hospital bed and tells her he doesn't know where they're going, but he feels safe with her. And like the title says, it's crazy, and it's stupid, but it's love.
As Dexter drives the Slice Of Life at high speeds in what I assume is the Gulf of Mexico, DVO tells us that fear and love are the strongest emotions, and what's more, they can make you do crazy things - like tell your own brother you're in love with him, or put your own life at risk to hunt down the man who took away your "beloved." Well, it's generous of Dexter to equate Deb's gross and wrong feelings with his actions that led to Rita's death, although I suppose he doesn't know just how popular the latter development was with the viewing audience. Having covered love, it's time for fear, and to address that, we pan back to see Hannah cowering in the back of the boat, life jacket clenched so hard it's begging for mercy. DVO goes on that another crazy thing is to do something for the sake of love that scares you to death as Hannah continues to turn shades of green that may not even have names yet; she eventually prevails on Dexter to take a short break.
After he cuts the engine, he sits with her, and after letting us know that Jamie has taken the kids back to Orlando (wonder how Dexter is justifying getting rid of Harrison this time), she apologizes, saying she thought she was over her fear of the water, but it turns out her continued phobia is at least understandable, given that her childhood swimming lessons consisted of her father taking her to the local pond and throwing her in. On top of everything else, this is the backwoods of Alabama we're talking about, right? I'm an expert swimmer and you couldn't pay me to dip a toe in water there. I might not get it back. Dexter, seemingly sincerely, remarks that that's horrible and asks where her mother was, and Hannah admits that she was there, but her father wouldn't let her intervene. "Six years old, and I already knew what it felt like to be dying." I can only imagine Hannah's Barbie endured some interesting experiences after this. Apparently Hannah lost consciousness, coming to later on the dock to discover that her mother's screams attracted a fisherman who saved her life, and I don't know what happened after that but I hope they had CPS in this Podunk town. Hannah asks if Dexter's ever been comparably scared, and he's slow to respond in the negative; Hannah picks up on his hesitation and assures him he can talk to her about stuff like that. He says he knows, and struggles with whether he should spit it out, but his phone beeping allays any decision. He tells Hannah it's work, and he should get back; without further discussion, he walks to the front of the boat and drives off. We get about ten seconds of them riding off, and it's a beautiful shot so I don't begrudge it, but it does get my filler alert tingling.