Prime Video has just added a very fun new action series

The latest show from Guy Ritchie, the series is streaming now in its entirety.

A quasi-prequel to Ritchie's Robert Downey Jr-starring Sherlock movies, the 1870s-set show sees a 19-year-old version of Holmes (played by Hero Fiennes Tiffin) sentenced to prison after a minor misunderstanding.

Struggling with guilt over the accidental death of his sister when he was a boy, Sherlock is freed from jail by his UK government employee older brother, Mycroft (Max Irons), and given a job working as a porter at Oxford University.

Despite trying to keep his head down and stay out of trouble, Sherlock's intellect and wit capture the attention of James Moriarty (Dónal Finn), an Irish student at Oxford, who similarly feels like an outsider.

It isn't long, however, before Sherlock, his family (including his father Silas, played by Joseph Fiennes), Moriarty and a young Chinese princess (Zine Tseng) all find themselves entangled in a mystery, with surprisingly far-reaching implications.

Young Sherlock Review

Yes, there's already been plenty of Sherlock Holmes adaptations in recent years. While BBC's Sherlock with Benedict Cumberbatch is the most famous, there have also been shows like Elementary, Watson, The Ireegulars, and Sherlock & Daughter, on top of Guy Richie's two Sherlock Holmes movies with RDJ.

Yet, to director Guy Ritchie (returning to the Sherlock world) and creator Matthew Parkhill's credit, they somehow mine fresh life and energy from well-trodden source material in Young Sherlock.

There's good humour to be found in meeting the lead character, someone we know will go on to become renowned for his genius, at the age of 19 and at rock bottom, surrounded by adults who constantly underestimate him.

Hero Fiennes Tiffin makes for an effortlessly commanding lead, conveying Young Sherlock's intellect, sly humour and inner darkness.

That said, the show is almost stolen by Irish actor Dónal Finn, who plays James Moriarty. While the character is commonly depicted as Sherlock's arch-nemesis, here they are best pals.

Both outsiders at Oxford - Sherlock because he is employed there as a porter, Moriarty because he is Irish - the pair form an oddly touching bond, even though their friendship is laced with tension, as we know from other adaptations of Moriarty's darker streak.

At eight episodes, the series' story feels slightly overstretched. That said, Parkhill delivers plenty of mini-mysteries and twists throughout, so that the plot never truly lags.

All the while, Ritchie and his fellow directors on the show do their best to keep the energy levels high. This is achieved through well-staged action set-pieces and fun anachronistic needle drops a la Steven Knight's work, like House of Guinness and Peaky Blinders.

Young Sherlock Interviews

JOE caught up with creator Matthew Parkhill and several of his cast in Young Sherlock.

While the show had its origins in Andrew Lane's Young Sherlock Holmes series of novels, Parkhill told us that the mysteries within his action-adventure are original.

"What happened was I got on board the project, and I read the [Andrew Lane] books, which I loved, and I gave them to my daughter, who was 14 at the time, and she loved them," he explained to JOE.

"But when I came back to the producers and to Amazon, I was like: 'I kind of want to do something a bit different.'

"Andy... his Sherlock is a 14-year-old schoolboy... I was very conscious of Young Sherlock Holmes, the Barry Levinson movie, the wonderful movie.

"I knew I wanted Sherlock to start in prison. I knew I wanted to explore the idea of loss of a sibling, and this dysfunctional family and the Butch/Sundance-esque relationship [between Sherlock and Moriarty], so I just took a different starting point.

"I just wanted to take it in a different direction. Everything in the show came out of the writer's room, basically."

As for how Hero Fiennes Tiffin became cast as Young Sherlock, he had previously collaborated with director Guy Ritchie on The Ministry of Ungentlemanly Warfare.

Hero Fiennes Tiffin in Young Sherlock

"I guess you'd have to ask [Guy], but from what I've heard, I think he was always rooting for me to play the character," Hero told JOE.

"I must have passed the Ritchie test on the first time round, on Ministry," he quipped.

"When people ask me why I took on this role, I think the more appropriate question is: 'Why the hell not?'

"Guy's always been one of my favourite directors. He was always at the top of my list for directors I'd love to have worked with.

"It was really nice to work in a smaller role with him on Ministry of Ungentlemanly Warfare to see how he works before stepping into this.

"I love his style, and I love how he works.

"Sherlock's one of my, and everyone's almost, favourite characters. I've always been a fan, so it was just a no-brainer."

The series is also a family affair in that Hero's real-life uncle, Joseph Fiennes, plays Sherlock's father Silas.

On how he became involved with the project, Joseph said: "[Hero] was cast, and it was a lovely idea, a notion that I might be invited in to play his dad."

Describing this opportunity as a "gift", he added: "We know each other, we're so familiar. I grew up holding Hero in my arms. He's probably bored of hearing that," to which Hero replied, smiling: "No, I'm never bored of hearing that."

Joseph continued: "And it's lovely seeing him flourish into this leading man."

That said, The Handmaid's Tale star was also drawn to the project on account of Parkhill's "vision of reinventing this tale" and "going back to the origins of what makes this amazing genius tick".

"There are so many Conan Doyle themes within here about control and chaos and imagination and intellect versus spirit."

Dónal Finn and Hero Fiennes Tiffin in Young Sherlock

Speaking of Moriarty and Sherlock's relationship in the show, Dónal Finn said:

"What's amazing... is that, in their personalities, you recognise Sherlock at this age, Moriarty at this age, and you go: 'That feels true to that person, way later in their life.'

"But what's unlikely is the friendship, you know? You're really serving the truth of those two characters, but what is surprising to us as an audience is that they're friends.

"And I think that helps subvert any kind of ideas or anticipation about playing the role."

Finn also said Moriarty's Irishness was key to his portrayal of the character.

He explained: "I used to watch these videos of Eamon Kelly, the seanachaí [a traditional Irish storyteller], and his ability to hold a room and to look after every detail of the storytelling process is magnetic.

"And if it fell into the wrong hands, it's manipulative because it's so compelling.

"So, I thought [about] Moriarty's ability to move through all these circles and the places that he gets called out in, like: 'You shouldn't be here.'

"There's a confidence and an ease [to him] that I think did resonate with me as being Irish... Beckett says: 'Dance first, think later.'

"He just wants to do things for the craic. He has a seize-the-day kind of energy."

The cast of Young Sherlock

Finn's co-stars are full of praise for the young star.

Hero said: "Dónal is… a lovely guy, but he's just such an exceptional actor.

"When we did a chemistry read… I was doing chemistry reads for a few different characters, and Dónal came in towards the end of one day. I just remember, within seconds, thinking this guy is going to make me look really bad if I don't bring my A game.

"He's an incredible actor, and he lives for it. Acting is his passion, and it shows, and I feel like I learn a lot from him."

Zine Tseng also described Dónal as a hugely "passionate" actor, while Max Irons told JOE: "I think he is the most fabulously nimble, imaginative actor out there; he seizes every opportunity and elevates it.

"To the moon for that guy, I think. He's everything… and super precise, and also the nicest guy around."

How to watch Young Sherlock

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All eight episodes of Young Sherlock are streaming on Prime Video now.