"Let's focus on the fact that we have no wands, no brooms, no means of returning to our time, all we have is our wits…. and we have to stop her."
-- Scorpius Malfoy (CC4.2)
30 October 1981
Left stranded at Aviemore train station in Scotland by Delphi after the destruction of the Experimental Time-Turner, Albus Potter and Scorpius Malfoy are lost. From a chance remark by the station master, Albus realises where and when they are in Time (CC4.2).
He now thinks that Delphi’s plan is to prevent Lord Voldemort trying to kill the infant Harry Potter and being destroyed by the rebounding curse – by killing Harry herself to save her father. Feeling that it is their fault that Delphi has had the idea, Scorpius and Albus realise that, somehow, they need to try and prevent this happening (CC4.2).
Twenty-four hours before Voldemort is due in Godric's Hollow - 30th October 1981
This event takes place during the Voldemort Final timeline, as described in the essay "Albus Potter and the lesson in Quantum Mechanics" by Nick Moline.
Initially Scorpius Malfoy worries that he and Albus will look ridiculous when they try to find out where they are:
"Hello, Mr Station Master. Mr Muggle. Question: did you see a flying witch passing here? And by the way, what year is it?" (CC4.2).
This is similar to how Harry Potter felt when he was asking the station staff at King's Cross where Platform 9-3/4 was located (PS6).
Scorpius feels responsible for having told Delphi that prophecies can be broken (CC3.20) and Albus worries that his father will blame him for everything that has happened.
From the Web
Pottermore: Harry Potter and the Cursed Child
The theatre production opened in the West End of London at the Palace Theatre on 30 July 2016, with Sam Clemmett in the role of Albus Potter and Anthony Boyle as Scorpius Malfoy: Harry Potter and the Cursed Child, Parts One and Two