âSherlockâ fans got a shock on Sunday (8 January) night, when the rumours that the detective and Mycroft have a secret sibling were confirmed.
However, it wasnât the brother everyone had been expecting - instead, we were introduced to Euros, their sister.
Actress Sian Brooke is playing the mysterious addition to the cast, and while weâll have to wait to find out more about the character, we can tell you about the actress herself.
So, in the immortal words of Nikki Grahame, who is she? Get to know her with our nine facts in 90 secondsâŠ
1. This is far from her first TV role
Viewers might recognise Sian from - *deep breath* - âCape Wrathâ, âMeadowlandsâ, âDoc Martinâ, âNew Tricksâ, âVexedâ, âSilkâ, âGarrowâs Lawâ or âFoyleâs Warâ.
2. Sianâs most recent TV role was in âNot Safe for Workâ
The actress played Martine in the Channel 4 comedy.
3. Her stage credits are also impressive
Sian has appeared in a number of plays, including various Shakespeare productions. In 2009, she played the female lead in the Royal Shakespeare Companyâs âRomeo And Julietâ, and has also starred in âKing Learâ and âA Midsummer Nightâs Dreamâ.
4. Sheâs already worked with Benedict Cumberbatch
Yes, on another Shakespeare project. Sian starred opposite the actor, playing Ophelia, in the Barbicanâs 2016 production of âHamletâ.
5. Sian was also in the first episode of series four
In the final moments of Sundayâs show, it was revealed that the woman John Watson nearly cheated on his wife with was actually Euros in disguise.
6. Her real surname is Phillips
She changed it to avoid confusion with the prolific Welsh actress.
7. Her screen debut was in a Disney series
She starred as Krista in the 2002 mini-series âDinotopiaâ.
8. Sheâs good at keeping secrets
We are, admittedly, making an assumption here but Sian was first spotted on the âSherlockâ set way back in June last year. This means sheâs known all about the seriesâ biggest secret - so far - for months. And we havenât heard a peep about it.
9. She could have a huge part to play in the much-hyped series finale
Sundayâs (14 January) episode is so epic that itâs being simulcast in cinemas up and down the UK. And judging from comments Mark Gatiss and Steven Moffat have made, carnage is in store.
Given that the closing scenes of last weekâs show saw Euros firing a gun at John Watson, weâre going to hazard a guess, and say that sheâll probably have a lot of involvement in the events that occur.