(I've left that title...it will do!)
So here we are then, the culmination of four series of Sherlock:
Finally we meet the girl on the crashing plane.
We are also introduced to her connection with Moriarty.
We get our first view of the Holmes family home movies and how Mycroft is affected by them.
So, we learn that the 'East Wind' is supposed to have been secured somewhere.
Sherlock confirms' I have a sister' and also that she was incarcerated from an early age.
So now Mycroft becomes the client, following on from Mary's stint in the chair.
Sherlock demands the whole truth. So we get the story of Eurus. Sherlock wonders why he can't remember her.
Mycroft explains about the ghost story he used to tell Sherlock, it was his way of looking after him, with the use of key words.
We hear about the super intelligence of Eurus.
Mycroft says that Sherlock was made by his memories of Eurus, we see some flashback footage.
We learn about Musgrave hall and that Sherlock played among the funny grave stones.
Sherlock remembers the song. He is starting to remember his childhood... 
We hear about 'Redbeard' and how Eurus used to say the song was the key.
We also hear about 'drowned Redbeard'.
Sherlock was traumatised by the loss of Redbeard, the loss stopped him being emotional. He even forgot Eurus.
Mycroft explains what he told his parents and why. We get the significance of Uncle Rudy.
We hear all about Sherrinford. Mycrofts insists it cannot have been Eurus that Sherlock and John met...butt hen the drone arrives with the song.
On the boat we hear about the secrecy of Sherrinford. The pirate theme is continued wit the 'Sherlock the pirate' comment.
We get an example of 'hiding in plain sight', with Sherlock managing to slip the net.
John knows that security is compromised.
Mycroft makes(as it turns out) a rather ghastly prediction about the governor not leaving the island.
Sherlock is struck by the violin playing of Eurus. Eurus plays the song as soon as he arrives, Sherlock gets a flashback.
We see Eurus declaring she is too clever.
Eurus gives Sherlock a violin. We learn she taught him to play. Eurus says Sherlock does not really know about Redbeard. 
Eurus asks Sherlock to play for her. "Play you." Sherlock plays the woman's theme and Eurus appears to deduce that Sherlock has had sex.
The Governor reveals that Mycroft gave Eurus Xmas presents and particularly a visitor.
Eurus reveals that Sherlock was her favourite. She made him scream all night because of Redbeard.
Sherlock says he remembers...but Eurus says he knows nothing.
John tries to warn Sherlock, he realises the governor is compromised. Who is in charge of Sherrinford?
We hear Moriarty...he appears on screen with the iconic ' Did you miss me?'
Poor John gets belted again!
We are then taken back to Xmas day 5 years earlier and shown how the ball rolls with Moriarty.
Mycroft tells Moriarty how Eurus helps the government. Moriarty is given the link to Sherlock...
We see the connection between Eurus and Moriarty. Eurus gives Moriarty ' Redbeard'.
Sherlock states that 'Family is always difficult'...especially when Eurus is in control.
We get the link to the 'girl on the plane' and Moriarty's messages.
The 'girl' states "I'm not supposed to tell my name to strangers."
Eurus talks of Mycroft bringing her treats and explains about Moriarty's messages. She tells of " the girl alone in the sky with nowhere to land."
We get another grizzly premonition form the governor: " Eurus will kill her", in reference to his wife. He asks John if he is married. The Governor then asks to be remembered...and he will be.
Eurus applies pressure to John.
John had looked to Sherlock before he pointed the gun at the governor. Sherlock reciprocates by looking to John, who tells him he should probably just take the gun.
Eurus reminds them of the "very scared girl on the plane."
Eurus states she was the only one to solve the Evans murder. 
Eurus warns Sherlock he may have to choose which friend to keep.
John says he is trying to save ' a little girl on a plane' and they have to be soldiers, Mycroft admires his priorities, tho John acknowledges they got a woman killed.
Mycroft cannot resist joining in Sherlock's deductions about the Garridebs.
John nearly cracks. Sherlock reminds him about playing soldiers and John stands to attention.
' The girl' now says she's " very frightened."
Smart Mycroft looks at the coffin lid and realises this whole scenario is all about Sherlock.
John states that it is 'Irene Adler' who loves Sherlock. He also moans that Sherlock never answers his phone.
Sherlock is emotionally broken by what Eurus makes him put Molly through...John helps him up.
Eurus warns Sherlock he has to choose between Mycroft and John.
Sherlock sees right through Mycroft's performance, Mycroft is trying to help Sherlock.
Eurus tells us that Moriarty knew who Sherlock would choose.
John knows that Mycroft is right about saying it is John's duty to sacrifice himself. Mycroft points out it is not John's decision and he explains why it is all his fault,
Sherlock looks to John, he comments how brave the governor was and he refuses to play ball with Eurus...
Eurus will not let Sherlock die without knowing about Redbeard.
Sherlock dreams of Redbeard. He is woken by 'the girl on the plane'.
Sherlock asks John if he is ok.
John finds small bones, as Sherlock finds 'Redbeard's' bowl.
'The girl' asks who Redbeard is.
When Sherlock sees Musgrave he says " I am home".
Eurus explains how she is Moriarty's revenge and that Sherlock must find Redbeard. She cites The Musgrave Ritual as Sherlock's first case and 'The Final Problem'.
The song is playing and Sherlock gets another flashback. 
John realises about the bones. Sherlock is still sure that Redbeard was his pet dog.
Eurus explains all. We see young Eurus playing with a toy plane.
Sherlock finally gets it. "Victor" His best friend.. We see Victor as Redbeard the pirate.
Eurus explains how she wanted to play, too. She sings " I am lost, who will find me?"
Eurus explains how all through Sherlock's life, he has been obsessed with 'deep waters'.
Eurus says she never had a best friend. She had " no one". We get an image of adult Sherlock seeing child Eurus with a plane and saying "Play with me, Sherlock."
Sherlock links the 'no one' to the funny headstones. "Okay, let's play" he tells Eurus. He knows if he solves the problem he will save 'the plane'.
Eurus says " I am lost without your love".
Sherlock connects the 'little girl on the plane' with Eurus. "Tell me your real name".
Sherlock tells Eurus to open her eyes and she will see he is there. She is "not lost anymore." He explains to her how "You just went the wrong way last time".He asks her to help him "Save John Watson".
Sherlock correctly uses Greg's name for the first time and Greg reciprocates by calling Sherlock a good man.
Sherlock defends Mycroft against Mummy.
Sherlock knows how to reach Eurus,
John calls Sherlock round to watch Mary's video. 
Mary has left a message for the boys, reminding them of their importance...we do see Rosie, but it's all about 'the cases'....

And that's all folks.
That's me backing out.
I haven't made the links...just pointed out what I think is important.