A "very rare" nerve agent". That is what the UK's interior minister says was used to poison a former Russian spy and his daughter.
Sergei Skripal and his daughter Yulia were found unconscious on a park bench in the British city of Salisbury on Sunday.
It follows several other mysterious deaths of Russians in the UK over the past few years.
Some had defected to Britain and had made allegations against President Vladimir Putin or his country's security services.
Those accusations often involved political assassinations, killings of civilians in bombings and running multi-million-dollar corruption rackets.
So, what will be the implications of this latest attack? And what steps will Britain take to prevent such killings in the future?
Presenter: Adrian Finighan
Bill Browder - CEO and cofounder of Hermitage Capital Management
Annie Machon - former MI5 intelligence officer
Samuel Greene - director of Russia Institute at King's College London
Source: Al Jazeera News