This week John Byrne takes in a documentary about Dublin's Glasnevin cemetery, the finales of two US dramas, a new series exploring science fiction, and Olly Murs being embarrassed by Graham Norton.

Reviewed: One Million Dubliners (Thursday, RTÉ One); The Leftovers (Tuesday, Sky Atlantic); Legends (Wednesday, Sky 1); Tomorrow's Worlds: The Unearthly History of Science Fiction (Saturdays, BBC Two); The Graham Norton Show (Fridays, BBC One)

After reading some rave reviews when it was originally released a couple of months ago for the cinema, I was really looking forward to seeing One Million Dubliners (Thursday, RTÉ One). What I wasn't expecting was a documentary that was incredibly poignant, hugely moving and a quite remarkable study of a cemetery and one man's relationship with it, and with life itself.

Beautifully shot and deftly directed by Aoife Kelleher, it set out to explore the life and death stories around Glasnevin Cemetery, where 1.5 million people lie buried. The good, the bad, the great, the unknown – all former human life is here, ranging from famous historical figures to hundreds of stillborn babies, mostly in unmarked graves. The story of Glasnevin and its inhabitants is told with a mixture of love, humour, dedication and eccentricity, but at its centre is Shane MacThomais, the cemetery's historian and tour guide at the time this documentary was being filmed.

He's just one of several fascinating cemetery staff who were interviewed for One Million Dubliners, but his sudden death last March, just as the film was wrapping, resulted in his funeral becoming a stark coda at the end of this remarkable film.

An uplifting and hugely moving experience, One Million Dubliners is a credit to all involved, and a compelling snapshot of Shane MacThomais' life, whose every moment on-screen is both a pleasure and a source of sadness. If you haven't seen it already, it's on the RTÉ Player for the next couple of weeks. Oh, and go visit a grave. It's good for you.

It seems almost frivolous to move on, especially to an American drama series such as The Leftovers (Tuesday, Sky Atlantic), which is the story of what happens in a small, upstate New York town in the aftermath of The Sudden Departure, when 2% of the world's population inexplicably disappeared in an instant.

The show's first, often baffling season came to an end and the final ten minutes were a jaw-dropping blend of despair and raging anger, but ultimately a chink of hope shone through the chaos. Which was a little unexpected given the downbeat rhythm of the show so far.

The spark for the dramatic finale came from Guilty Remnant (GR), the cult formed in response to The Sudden Departure, whose members placed lifelike dolls of the Loved Ones (those who had disappeared) in their former homes, causing an outbreak of extreme anger from survivors that resulted in murderously violent attacks on their members and the burning down of the houses where the GR lived in communal existence.

Carrie Coon has been outstanding as Nora (see clip), a woman who lost her husband and two children – everything, basically - to The Sudden Departure, and she was a star turn again in this episode, as Nora broke down after seeing her mannequin family, and was determined to commit suicide until she found an abandoned baby in a basket on the doorstep of her policeman lover, Kevin (Justin Theroux) Garvey.

I don't expect many answers from this show – it's clearly not about that, but how people react differently to their situation, and the knock-on effects it has on society – but the first season of The Leftovers was fascinating, and almost as baffling as that truly bizarre cult classic, John From Cincinnatti, a series that made Twin Peaks look like TOWIE. Roll on season two.

Another show just finished its first run is Legends (Wednesday, Sky 1). But we're dealing here with something far removed from The Leftovers as Sean Bean's Martin Odum is an undercover FBI agent who discovers that nothing about his life is as it seems.

I had assumed that this show, which bounced between case of the week and Odum's search for the truth about himself, was ending after one season as the story had pretty much played itself out. But apparently TNT, the US cable network behind the show, has yet to make decision one way or the other.

Presumably that's why, after all the key loose ends had been tied together, Sean Bean's character ended up on the run for a murder he didn't commit. Handy, of course, if a season two does happen, but no way to end the show if this is to be its final episode.

The geek in me was in overdrive in advance of Tomorrow's Worlds: The Unearthly History of Science Fiction (Saturdays, BBC Two), a new five-part exploration of a genre that goes to infinity and beyond. It crammed so much into its opening hour that I had to pause it several times just to take it all in.

Host Dominic Sandbrook is a historian and author, as well as an experienced broadcaster on both radio and TV, and presumably is also a keen fan of science fiction. Given the subject matter, that has to be the case.

Starting off with the ubiquitous Star Wars, things got interesting with some Jules Verne and Moliere references, before we hit US pulp magazines and then moved on to TV shows such as the idealistic Star Trek, the optimistic Battlestar Galactica, and its more downbeat 2003 reboot, which reflected the USA's post-9/11 world view. It was pointed out, quite correctly, that although science fiction is about the future, it tends to do so from a very contemporary perspective.

As always with such shows, there were more talking heads than clips, but when the guest list includes the likes of William Shatner, John Carpenter and Neil Gaiman, it's impossible to complain.

Stanley Kubrick's visual masterpiece 2001: A Space Odyssey was also put in context, while other cinematic science fiction classics such as Dark Star and Alien also got the once-over.

Books, where it all began, finally enjoyed a close-up with the likes of Frank Herbert's Dune and The Left Hand of Darkness by Ursula K Le Guin, while the over-hyped Avatar and the truly unique Hitchhiker's Guide to the Galaxy also got a mention.

This show won't convert anyone who isn't already at least disposed towards science fiction, but for fans who are perhaps only aware of one aspect of the genre, Tomorrow's Worlds: The Unearthly History of Science Fiction offers a rounded insight that could well turn an interest into a full-on obsession. And where's the harm in that?

Finally, a sympathetic nod to Olly Murs, who was embarrassed yet again - it was with Mila Kunis last year - on The Graham Norton Show (Fridays, BBC One) when Graham showed a tweet where Olly expressed his excitement at the prospect of meeting fellow guest Jennifer Aniston. Later, she gave the singer his Rear of the Year Award, but only after an embarrassing shot of the Murs' bum was shown on screen. Who'd want to be famous? Be careful out there . . .

It was all good fun though in what was yet another spectacularly enjoyable show, with Dustin Hoffmann and Judi Dench – who recently worked together on a BBC adaptation of Roald Dahl's Esio Trot - forming an impressive double act on Graham's couch, while Jason Bateman just looked weird with all that hair.

I remain in awe of Norton's ability to juggle his guests, get a lot of laughs, and make every 45 minutes feel like your best-ever trip to your Auntie's. It's a remarkable show that should, by now, have cult status amongst American stars who must find it a refreshing change from the stale US chat show circuit.

John Byrne