While Bruce walks through Gotham, spotting his ex (I believe) on the way, he speaks with Alfred over the phone about the plot of land that he lost the Hatter at last issue, and finds that there are no viable clues in the paperwork, as it's all tied up in Hatter's "company." Luckily enough, a local nightclub is also listed on the papers as being part of the ownership group, so Bruce figures that it's a good enough place as any to start looking for hatter.
Bruce finds Tweedledee inside the club, here's a sob story, but threatens him, while swiping his cellphone during the process. The phone ends up getting remotely wiped, but Bruce manages to use it and track it down to a warehouse near a cell tower it was connected to.
Inside the warehouse, Bruce finds some of Hatter's goons lugging crates, typical goon stuff, then kicks some ass. Inside the crates are an assortment of weapons and tea, which Bruce tests to find it's ingredients varying from batch to batch with different mood alternating formulas. Basically, Hatter has a tea for any type of mood that strikes him, and he also has a lead pipe, which he swings at Bruce's head.
When Bruce comes to, he leaves the warehouse and finds Catwoman on a nearby rooftop. Selina does some flirting, which isn't responded to by Bruce. She figures he may have found a "Mrs. Batman" and proclaims that their fun comes from not knowing each other, so on and so on.
Back to Hatter's childhood, turns out he was diagnosed with a testosterone deficiency, and essentially stopped growing. Hatter's parents took him to a doctor after he expressed not wanting to be left behind when all his friends were growing up, and was prescribed a potentially psychologically dangerous drug for his condition, but didn't take it yet... that's before his crush Alice told him she didn't like him "like that."
So, whatever Hatter's plans are, seem to be ready, and he goes off to fetch his Alice. At her house, he pays off her deadbeat looking husband to scram for an house, and find his alice... old, tired, smoking, and clearly a few kids deep. Long story short, she gives him a line about how he never grew up, Hatter trips balls on some tea, and then "frees" her by bludgeoning in her head with an iron.
Bruce then has a flashback to his parents, telling him that their only wish is that someone will come to know him, and he'll be able to share his life with them... of course this means he heads to his ex, Natalya's apartment, goes "Hey, check this out," jumps out her window onto the batwing's wing, flies her to the Batcave and goes "I'm Batman, baby!" ...well, he doesn't say that, but that's what he does.
Then finally, after Hatter freaks out a bit about his Alice being gone and needing to find a new one, then we see that Hatter did eventually take that drug as a child.