So far in season six of the, um, edgy Showtime drama (episode three airs tonight), Deb has stolen the spotlight.
She's been promoted to lieutenant of the homicide squad and received a marriage proposal. She's become a YouTube sensation and the subject of dirty limericks.
Unfortunately, what you've seen is all you're going to get.
Carpenter won't give away any plot secrets.
"Every time we get a script, we get a memorandum instructing us not to talk about it," she says.
She also won't discuss her relationship with Dexter star Michael C. Hall. The couple eloped on New Year's Eve in 2008 and divorced two years later.
"That's intensely personal," she says. "We're better friends now then we've ever been. In fact, I had dinner with him on Saturday night with friends. It has not impacted at all our ability to work together."
What she does reveal is that Dexter, despite its convincing pink flamingo decor, is shot near Los Angeles, not in its notional setting of Miami.
"We would go through about three hours of hair and makeup a day, it's so muggy in Florida," she says, "especially in the summer. We shot the pilot there. It took about an hour to shoot a short scene of Michael in his car because he had to change his shirt three times."
Carpenter is on the phone, driving to the E! studios for a TV interview. As she pulls up, her voice suddenly grows Elvis-sighting animated.
"The Glee Project [winners] are coming out," she trills. The volume dims as she turns from the phone to shout, "I watch you guys all the time. You're terrific!"
Eventually she gets back on the line. "I don't watch Glee but I watch The Glee Project" on the Oxygen channel, she says. "They send shivers down my spine."
Carpenter has a similar effect on Dexter fans. As well as the show's creators.
"When we saw Jennifer's audition, we all had the same reaction: 'We found her. There's our Deb,' " says executive producer Sara Colleton.
"Jennifer Carpenter has the unique combination of toughness, intelligence, humor, and vulnerability, all the qualities of Debra Morgan. Jennifer brought to life a character who only existed on the page, and now it's impossible to separate the two."
One of the uniquely convincing aspects of Carpenter's performance is how well she handles the action scenes. If you watch closely, most actresses playing law enforcement figures on TV run like supermodels tottering after a scarf. Carpenter looks like she'd have no problem overtaking a perp.
"I ran in the New York Marathon last year," she acknowledges. "It was my third. I was out to beat my personal best of 3 hours 30 minutes."
Carpenter ran cross-country in high school. Juilliard, it may surprise you to learn, has no athletic teams. You just assume they'd be Division 1.
"I didn't graduate," she says. "The summer going into my fourth year, I was offered a play at Lincoln Center. The day after that play closed I started rehearsals for The Crucible on Broadway."
The revival of the Arthur Miller play starred Laura Linney and Liam Neeson. "I showed up every day to watch them rehearse, whether I was on call or not."
When the show closed in 2002, she impulsively moved to Los Angeles to pursue TV and film work. She would land a breakout role as the title character in the 2005 film The Exorcism of Emily Rose, in which she spent most of her time in a long linen nightgown.
But that came only after years of scrambling to survive.
"I had no plan and no money," she says. "I was living on lawn furniture for about three months. I was looking for a job but it didn't happen until I started waiting table. I wrote a fake resume. I had to ask the other waitresses how to carry two plates at the same time.
"I waited on the Wayans brothers the night before I auditioned for [their film] White Chicks," she continues. "This was the third audition, and the night before they came in my restaurant and I waited on them. The next day they didn't recognize me."
Hard to believe. If Carpenter in person is anything like she is on the screen, she leaves an electrifying impression.
Contact staff writer David Hiltbrand at 215-854-4552, email@example.com, or @daveondemand_tv on Twitter. Read his blog, "Dave on Demand," at www.philly.com/dod.