Endeavour was commissioned by the ITV network after a one-off TV movie of the same title aired in 2011 to critical and popular acclaim.
Liverpudlian actor Shaun Evans, who reprises his role as Endeavour Morse, said he was pleasantly shocked that ITV picked up the show.
"I never thought it would go any further," Evans said on the phone from London. "Then I got the call that they wanted to make four more." Evans, 33, an impressive, deeply intuitive actor who has made Endeavour Morse very much his own, said a second season already had been green-lighted for next year.
The reason for Endeavour's success isn't hard to divine. It's written with meticulous care, insight, and eye for detail, and it features some of the best British actors, including Roger Allam and Anton Lesser.
But it's Endeavour's provenance makes it all the more fascinating: It's the second spinoff of one of the most beloved TV mysteries from the 1990s, Inspector Morse, which featured the inimitable John Thaw as the title character and Kevin Whately as his oft-mistreated bagman, Sergeant Robert Lewis.
Adapted from the novels by mystery writer Colin Dexter, Inspector Morse ran for 33 feature-length episodes from 1987 to 2000, ending with Morse's death from a heart attack. (Thaw, who was gravely ill during filming of the last season, died 15 months later of cancer.)
A first spinoff, Inspector Lewis, premiered in 2006 and stars Whately as Morse's replacement.
Endeavour is unique because it promises to clarify one of the greatest mysteries of the Morse character: his youth.
Morse already is in his 50s when we meet him in the Dexter novels and the show. An emotionally closed-off introvert, he reveals little about his past. He tells no one his Christian name - his lover doesn't know it, nor does his partner Lewis - until he's on his deathbed!
We know Morse was a middle-class kid from a broken home who won a scholarship to study classics and literature at Oxford. (His major is identified as "Greats.") More than capable, he nonetheless fails to complete his degree, joining the Oxford police force instead.
The middle-aged Morse lives alone and would rather bury himself in the London Times crossword puzzle than ask a woman out on a date. He is afraid of women and prone to hide his anxiety by being patronizing, even caustic.
"He's someone who seems frozen in the past," Evans said of the older Morse, "and he doesn't get people."
With few clues to go on, Evans had a hard job of reverse-engineering the character.
"What are the factors in his late 20s that would make him a heavy drinker and kind of terrible with women, yet so great at his job?" Evans says he asked himself. "Who is this person who finds solace in art and opera . . . rather than other people?"
Evans closely studied the Dexter novels, but he avoided watching Thaw's series. "I don't see the benefit of doing a facsimile of what another actor was doing. . . . I mean I could only do a [terrible] version of Thaw! And it would shortchange the audience," he said. "I thought the only way to make it good was to make it my own."
Endeavour introduces viewers to two characters later to figure large in Morse's life: pathologist Max DeBryn (James Bradshaw) and a young, naive constable named Jim Strange (Sean Rigby), who will be Morse's superior 25 years down the road.
The most important character, however, is young Morse's boss, Detective Inspector Fred Thursday, played by eminent stage actor Roger Allam. Thursday is Endeavour's mentor and spiritual adviser. Allam, currently on stage as Prospero in The Tempest at Shakespeare's Globe Theatre in London, said Thursday is the positive, encouraging father Endeavour never had.
"I think Thursday is shrewd enough to see something in young Endeavour that is very often lacking in a police station," Allam, 59, said in a phone chat. "The police often get bogged down in procedure, and what Endeavour brings is this more imaginative, instinctive way to deal with crimes."
It's an especially good talent to have in Dexter's Oxford, where the killers are, more often than not, brilliant Oxford professors who like to baffle the cops with cryptic clues, unbreakable codes, wordplay, and obscure literary allusions.
That's when Endeavour puts on his supersleuth cape.
Premieres at 9 p.m. Sunday on WHYY TV12 and airs on consecutive Sundays through July 28.
Endeavour, Series 1
Includes the 2011 TV movie. Due July 16 from PBS Video ( www.shoppbs.org/; $39.99; not rated).
Contact Tirdad Derakhshani at 215-854-2736 or firstname.lastname@example.org.