Looks like the toxin was planted in the daughter's luggage in Russia.

Nerve agent planted in luggage of Russian agent's daughter: The Telegraph https://a.msn.com/r/2/BBKhLho?m=en-us&a=1

So something she would handle or unwrap once she was with her father. 

And another death.
UK calls death of Russian businessman Glushkov a homicide https://a.msn.com/r/2/BBKjiNz?m=en-us&a=1

Skripals poisoned from front door of Salisbury home, police say


https://www.theguardian.com/uk-news/2018/mar/28/skripals-poisoned-from-front-door-of-salisbury-home-police-say

Anti-RU crap?

The UK gov spread chemicals to see what effect it would have on the populace :

https://www.independent.co.uk/news/uk/politics/how-the-british-government-subjected-thousands-of-people-to-chemical-and-biological-warfare-trials-10376411.html

Can you say "Fort Detrick", "Porton Down".