In March, The Guardian ran a true crime reporting series called How to Solve a Murder. The four-part series chronicles efforts to solve the 35-year-old unsolved murder of Kari Lenander, a teenage girl, in Los Angeles in 1980.

In some ways, How to Solve a Murder is just an investigative online story with original art and interactives. But there’s a twist: The series is sponsored by Amazon. Amazon Studios commissioned it to promote Season 2 of its original drama Bosch (based on Michael Connelly’s bestselling series on L.A. detective Harry Bosch), which streams on Prime Instant Video. It ran on Guardian Labs, the paper’s branded content division.

This “investigative brand journalism…was a unique and exciting project for us here,” said Jill Hillbrenner, a branded-content strategist at Guardian Labs and the author of the story. “We needed to find content that supported the second season of the Bosch series, but we could do that in a very Guardian way, with all of the same empathy and human interest components we’d do with any other Guardian storytelling.”

Amazon declined to comment for this story, saying: “We’re not inclined to discuss our marketing strategies/approach.” The company also did a sponsored three-episode podcast with Slate’s Panoply to promote the second season of Bosch.

Guardian Labs U.S., the paper’s content marketing division in New York, launched in 2015 and now has 22 full-time employees; it’s worked with clients like Ben & Jerry’s, HP, and Visa. Branded content is a key part of the company’s strategy as it aims to cut costs by 20 percent and find new revenue sources by 2019. Other large newspapers, like The New York Times and The Washington Post, have also launched branded content divisions.

In the case of How to Solve a Murder, Amazon came to Guardian Labs with a few basic guidelines, explained Rachael Post, The Guardian’s branded content director. The company wanted the series to be set in either Los Angeles or Las Vegas; it had to include a detective and a cold-case murder (for legal reasons, Guardian Labs couldn’t cover a case currently undergoing trial).

Guardian Labs ended up working with Detective Tim Marcia, a homicide detective for the Los Angeles Police Department and the co-owner of Behind the Badge Technical and Creative Consulting, a company that provides law enforcement experience to the entertainment business. Marcia is a consultant for Amazon’s Bosch. Amazon didn’t require Guardian Labs to work with Marcia, Post stressed, but he was able to speak about possible cold cases that were interesting within the LAPD’s history.

“As we were talking to him, we found out about this cold case murder from 1980,” Hilbrenner said. “We were not compelled to use it because of him or his status. But the case has essentially haunted him since he took it on in 2002. He and [Kari Lenander] would have been about the same age.” They attended rival high schools and hung out on the same stretch of beach in L.A.

“He was assigned to her case in 2002 and hasn’t been able to forget about it,” Hilbrenner said. “He’s trying to solve it before he retires in four years or less. We thought, in a small way, we could contribute to [solving it].”

The reporting process was similar to what it would be for any other investigative piece, said Hilbrenner. She conducted in-person interviews in L.A. and looked at original documents when possible. The difference came after the story was written: Guardian Labs showed it to Amazon Studios, which didn’t make any requests for changes. There was also an added layer of legal scrutiny, beyond the basic legal considerations that are required when reporting on any murder investigation. “We worked closely with our team and Amazon lawyers to make sure [it was totally clear] that this was branded content,” Post said.

This LAPD homicide detective is one clue away from solving a 1980 cold case. https://t.co/UraHe7uEow | @boschamazon pic.twitter.com/CeEDoXWNIf

— Guardian Labs US (@GuardianLabsUS) March 15, 2016

How to Solve a Murder doesn’t seem super-promotional or brand-focused, apart from the small “Paid for by Bosch/Amazon” at the top of each page and the disclosure at the bottom (“Disclosure: Detective Tim Marcia consults for Bosch, the Amazon Original Series. Stream the new season of Bosch on Amazon Prime on 11 March.”)

The positive focus on Detective Marcia (that’s him in the art illustrating this post) also comes across as a little unusual to those who’ve read a lot of true crime articles, watched Making a Murderer, listened to the first season of Serial, or followed The Guardian’s regular series, The Counted, which tracks the number of people killed by law enforcement in the U.S.: Frankly, the trend in cold-case murder coverage right now is to focus on missteps and unethical behavior by detectives, police, and other law enforcement officials. How to Solve a Murder, by contrast, includes a full section called “Inside the mind of a homicide detective.” (“Like many law enforcement officers around the country, Marcia is expected to stay strong under pressure — all while examining unthinkable crime scenes, comforting victims’ families, and prodding the truth out of killers. As he puts it: ‘It’s a tough job, but it’s an awesome job.'”)

“We wanted to showcase a good cop,” Post said.

The case hasn’t been solved. Guardian Labs’ series ends with Detective Marcia saying “he believes there’s enough to eventually solve it,” that he won’t forget Kari Lenander, and that he can’t “imagine giving up his hunt for the killer.” If Michael Connelly ended his books that way, Harry Bosch wouldn’t have nearly as many fans.

Still, How to Solve a Murder “exceeded all the metrics we’d set for it,” Post said, though she wouldn’t go into detail. (Part 1 of the series got about 3,000 Facebook likes and shares.) Guardian Labs promoted the series in paid social media posts and also did some unpaid promotion for it, featuring it online on the Guardian U.S. homepage and in the sports and arts and entertainment sections. The series, like other branded content, was always clearly labeled with Amazon’s logo and the Guardian Labs logo, Post said.

“With this one promoted Facebook post, it was clear that [readers] were reading the content, because they were commenting back and forth with each other with information that they wouldn’t have known unless they’d read through half or even three-quarters of the story,” Hilbrenner said. “They were seeing the post, going back through, and commenting. That told us we’d done our job.”

Guardian Labs hopes to do more projects like this, Post said. And she and Hilbrenner see How to Solve a Murder as a shift in branded content: more authentic stories that come about almost in “natural” ways and don’t simply consist of a media company promoting something that the brand is talking about on other channels.

“We can have objectives that walk side-by-side each other,” said Hilbrenner, “but, from the reader’s perspective, it’s not such a pointed relationship.”