Rumble in the jungle

Sigourney Weaver, who earned an Oscar nomination for her role in “Gorillas in the Mist,” narrates “Dian Fossey: Secrets in the Mist,” a three-part documentary that looks at the iconic primatologist 32 years after her murder. The film focuses more on her death than her mission to champion wildlife.

8 p.m., National Geographic

Nighty, knight

In their quest to find the Holy Grail, the Templars in “Knightfall” never cross paths with Monty Python, which is too bad; these sourpusses could use a few laughs. Producers of this relentlessly morose series are clearly seeking out the same audience that made “Vikings” a hit, but early episodes don’t offer any heroes we’re eager to ride with.

9 p.m., History Channel

Get happy

Just because Patton Oswalt voices an animated character who could have flown off a cereal box doesn’t mean his tricks in “Happy!” are for kids. This super-dark, often hilarious drama about a disgraced ex-cop wrangled into doing one last good deed for an imaginary “friend” is strictly for adults. Star Christopher Meloni taps his inner Bruce Willis and yippee-ki-yay’s his image as the bottled-up detective on “Law & Order: SVU.”

9 p.m., Syfy

Neal Justin