Produced by National Geographic, the series “Strange Days on Planet Earth” (8 p.m., PBS, check local listings) returns for a second season. Edward Norton hosts and narrates.

Clearly inspired by reports of rapid climate change, the series also offers many fascinating examples of complex interconnections in nature. Circumstances that harm one species affect others in dramatic, if not always obvious, ways.

The first segment takes us to Ghana, where animals like lions and hippos are disappearing quickly, while olive baboons are enjoying a population explosion.

One scientist theorizes that this unbalanced phenomenon may have something to do with the dwindling fish supply off Ghana’s coast. He has collected decades of data to argue that European and other Western industrial-fishing fleets have ravaged the supply of seafood, leaving many poor residents of Ghana to hunt for “bush meat,” the term for local protected animals. As their predators have disappeared, the olive baboons have flourished. In fact, they’ve grown so bold that they are now attacking farms and ruining crops. And that, in turn, forces folks to hunt for more bush meat. So, this thinking goes, lions are vanishing all for the lack of fish.

In another segment, residents of coastal Namibia have experienced massive fish kills as the sea turns yellow and the sky fills with a sulfuric stench. It’s a natural mystery that unfolds like a horror movie.

¢ “Secrets of the Dead” (7 p.m., PBS, check local listings) also begins a new season. Like “Strange Days,” it presents a scientific detective story. Unlike Norton, Liev Schrieber (“Manchurian Candidate”) lends only his voice to “Dead.” Perhaps forensic archaeology is less sexy than saving the planet.

Tonight’s “Dead” travels to Mexico City, where the remains of Aztec-era victims of human sacrifice have recently been discovered. Upon further investigation, scientists determine that many seem to be of European origins. This stimulates speculation that at least some in the party of Hernan Cortes may have met a grim fate at the hands of the Aztecs.

¢ Originally scheduled for May 7, the special “Inside a Cult” (8 p.m., National Geographic) has been moved up to coincide with coverage of arrests at the Texas polygamist compound. “Inside” talks to members and former members of a group in New Mexico called the Strong City Cult, where 56 followers worshipped their leader as a messiah and anticipated the end of the world on Oct. 31, 2007.

“Cult” explores ways that self-described messiahs often use sex rituals as a means of control and how family members and other skeptical outsiders are kept away. The camera crew for “Cult” spent time with the cult as the minutes ticked down to doom’s appointed hour. It also looks back at cults with rather unhappy End Times stories, including the mass suicide of 38 followers of Marshall Applewhite in 1997 and the more than 900 victims of Jonestown in 1978.

Tonight’s other highlights

¢ Country and hip-hop clash on “Wife Swap” (7 p.m., ABC).

¢ America votes and gives one singer the hook on “American Idol” (8 p.m., Fox).

¢ “MythBusters” (8 p.m., Discovery) examines legends of Alaska.

¢ A stalker takes an agent hostage on “CSI: NY” (9 p.m., CBS).

¢ Green falls under suspicion on “Law & Order” (9 p.m., NBC).

¢ Cash needs a crash pad on “Men in Trees” (9 p.m., ABC).