“I thought: ‘Oh, he’s going there—let’s do this,” said Cardenas of their first meeting. 

Cardenas, cofounder and CEO of humanoid startup Apptronik, wasn’t expecting a therapy session. But he talked openly, then provided Zeplain with a list of everyone close to him—his wife, his coworkers, his childhood best friends. Zeplain called them all.

The deal got done at a $250 million post-money valuation, and as of February, Apptronik is valued at more than $5 billion. Zeplain says he can’t always predict which businesses succeed, but he’s gotten quite good at understanding which people will succeed. “This is not one-size-fits-all,” said Zeplain. “Sure, there are certain tenets you can repeat and reuse. But this is a tailored approach to who someone is.”

Zeplain’s firm—which he cofounded with Andy Bursten in 2017—is Austin-based Mark VC (the name is stylized as “mark vc,” to signify a VC’s fundamental insignificance in a company’s journey). After backing companies like CrowdStrike, Reddit, Ring, Capella Space, and Anduril, the firm has reached an inflection point: Zeplain is not entirely a new manager anymore. And while known and admired in certain corners of the tech world, he’s kept quiet.

That’s in part because Zeplain is notably press-shy. The sole reason he agreed to talk to me is that we’ve known each other for two years and have spent hours together off-the-record. Over that time, I’ve learned that a growing number of venture capital stalwarts—from early Facebook backer Jim Breyer to legendary LP Scott Malpass—are watching him closely. Nearly everyone I spoke to for this story brought up the name Bill Campbell in reference to how Zeplain works. Campbell, long ago profiled by Fortune, was the defining CEO coach behind the rise of Larry Page, Sergey Brin, Steve Jobs, Jeff Bezos, and many more. A key similarity: Like Campbell, Zeplain’s toughness is only possible because of the depth of caring. 

And at a time when most VCs—and most businesses on the planet—are extolling their data-driven AI strategies or large-size funds, Zeplain stands out for emphasizing the person, not the numbers.

“When I meet somebody, the goal is: ‘I’ve known this person for two weeks, so how do I make up for lost time?’” said Zeplain. “‘How do I figure out how to cram 10 years of data? How do I learn things about this person I’d know only if I’ve known them for 20 years over a few-week period?’ You can never fully do that, but I can do it better than most.”

If you think this sounds warm and fuzzy, think again. Zeplain’s due diligence process isn’t for everyone, says CrowdStrike cofounder Dmitri Alperovitch. 

“In this environment, every investor is chasing the hottest company, so not every founder is going to be willing to go through that process with Adam,” Alperovitch told Fortune. “Not everyone is going to be willing to go through, for lack of a better word, a therapy session or agree to family members being interviewed, which is what Adam likes to do. He doesn’t get into every deal, but he gets into enough of them—and the right ones.”

‘Who is this guy?’

How much can you learn about a person, an entrepreneur, in just a few weeks? The answer, Zeplain says, depends on who you talk to and the questions you’re willing to ask. You have to engage directly with how people not only see themselves, but how those closest to them do. Zeplain talks to the entrepreneur, yes. But he also devotes hours to friends, family, colleagues, and spouses. He says you also have to talk to people whom the founder’s been in conflict with: Everyone from critics to ex–romantic partners to teachers and coaches are on the table.  

Zeplain’s looking for a 360-degree behavioral map that models not just how someone performs when things are going well, but how they show up when they’re stressed, cornered, or outright failing. The question, of course, is how Zeplain gets people to talk about the tough stuff. It’s about asking, but it’s also about intent. 

“Most people, when they truly know and care about someone, don’t just want to speak to the things that make that person look good,” said Zeplain. “If they can see that you’re already committed to their friend or colleague—if they feel like you’re just trying to best learn how to support that person—they’re radically open about their weaknesses. They just have to know you care about that founder and their success.”

CrowdStrike’s Alperovitch remembers Zeplain grilling him in 2016, when they first met. 

It’s an affectionate description from Alperovitch. Back in 2016, CrowdStrike hadn’t even hit unicorn status, and Zeplain was still in the earliest days of building Mark VC. Both at Fortune’s Brainstorm Tech, Zeplain and Alperovitch were sitting across from each other at an Aspen restaurant.

“It was like going through a waterboarding session,” said Alperovitch. “It was rapid-fire questions from Adam about everything from me to CrowdStrike. And I was like, ‘Who the hell is this guy?’” I’d never had that experience with an investor—most investors go deep on the business side, but it was all about me. It wasn’t typical for investors at all.”

That conversation was the beginning of Zeplain’s 2017 investment in CrowdStrike—at the time, $5.69 a share, at a $1 billion post-money valuation. CrowdStrike went public in 2019, starting at $34 a share and popping into the $60s. 

Adam Grant, New York Times bestselling author and Wharton organizational psychology professor, has known Zeplain since 2018. “It’s hard to get to know Adam without admiring his candor, and wanting to be more constructively challenging to the people around you,” said Grant. 

That candor, Grant says, is especially tough to find for people who’ve already achieved some measure of success. “As people start to attain some success, it’s very hard to find the people who will tell them the truth as they see it,” said Grant. “Part of the value Adam offers is that he’s an example of a category of givers I call ‘disagreeable givers.’” A disagreeable giver, Grant says, is “fearless about dishing out tough love, and keen to give the critical feedback you might not want to hear, but desperately need to hear. That’s what makes him cut from the Bill Campbell cloth, so to speak.” 

Dara Treseder, Autodesk CMO and Zeplain’s longtime friend and mentee, calls Zeplain to tell her the truth. 

“He’ll help me feel a little validated before he drops the hammer,” she said. “But he’s absolutely going to drop the hammer.”

‘The IRR Hall of Fame’

Venture capital is in something of an identity crisis—multibillion-dollar funds are raising questions about what the future of returns looks like. In that context, Zeplain’s approach is distinctly retro, said Scott Malpass, cofounder and managing partner of Grafton Street Partners and a Mark VC LP. Malpass is one of the few genuinely famous LPs in the industry: He spent 32 years as Notre Dame’s chief investment officer and helped reshape how endowments think about venture.

“I’ve hired and fired over 400 VC firms, and I admire people who become true partners,” said Malpass. “They care about me as much as I care about them; they’re fair and very transparent. Adam has all of that.”

Malpass said that Zeplain is as “close as anybody I’ve seen” to the founders he invests in, and that is the business. Zeplain has kept his funds relatively small. “Adam wants to be in the IRR [internal rate of return] Hall of Fame, not the AUM [assets under management] Hall of Fame,” said Malpass.

Once he invests, Zeplain operates differently than most VCs. He won’t, under any circumstances, take board seats. He’d rather hear whole stories, not the versions sanitized for a boardroom. His conversations with founders tend to be less about strategy and more about clarity—helping entrepreneurs think through what they’re actually seeing, rather than telling them what to do. The coaching is business-oriented, but it’s fundamentally psychological.

Jim Breyer—longtime legendary Accel investor and now running Breyer Capital, also an LP in Mark VC—says that venture’s paradigm shift serves Zeplain. This isn’t a tech and market-picking game anymore, Breyer told Fortune. The business is becoming something more interdisciplinary and human-centered.

“The need to coach entrepreneurial teams as they’re scaling will never go away,” said Breyer. “In fact, Adam’s skill set is more needed today than ever before, given how interdisciplinary so many teams are from the get-go. The empathy Adam embodies is more vital than ever.”

Daniel Breyer—Jim’s son, a Breyer Capital partner, and a published author—has been a mentee, then friend, of Zeplain’s since 2020. And he says Zeplain’s process (which he fondly describes as a cross between executive coaching and therapy) has no reason to scale. 

“When I imagine a very successful picture of Adam in 10, 20, 30 years, he’s doing exactly the same thing,” said Breyer. “He’ll keep just raising funds from the people he really wants to work with, and stay very careful on the deployment side.” 

This picture tracks with how Zeplain seems to see himself. 

“My job isn’t to solve the problem for the founder,” said Zeplain. “I believe my job’s to be the Windex on their windshield. To help them see more clearly, to see if we can solve something together. If we can, great. And if we can’t, my job is to hold them accountable and support them. I don’t judge my success by whether I can consistently solve the problem. I judge myself by, ‘Am I willing to have tough conversations when needed?’”