London (CNN) - It's more than a week in and questions are still swirling over how and why a former Russian spy and his daughter were poisoned in the cathedral city of Salisbury in southern England. Sergei Skripal, 66, and his daughter, Yulia, 33, remain hospitalized in "very serious condition."
On Monday, British Prime Minister Theresa May answered some of them by telling Parliament it was "highly likely" Russia was responsible for the "military grade" nerve agent attack on the pair. Russia's Foreign Ministry described May's strongly-worded statement as a "circus show" and the latest in a series of "fairy tales".
While Monday's developments are likely to plunge relations between the UK and Russia to a new low, a number of key questions remain unanswered.
How did the Skripals leave such a long trail of contamination?
It is staggering, but a statement Sunday from health authorities effectively said the pair were in contact with -- or carrying -- the poison for their entire Sunday afternoon trip. Authorities found traces in the Mill pub and the Zizzi pizza restaurant, as well as on the bench where the two began to lose consciousness. This suggests that they perhaps carried the poison with them.
But where did they become initially exposed and get their lethal doses? If they, for example, carried an infected package with them for the afternoon and then opened it somewhere, you would expect a larger concentration in one place. Yet health professionals talked about small traces in both the pub and the pizza restaurant. So, they either got their main dose on the bench -- say from inhaling a cigarette or opening a package -- and immediately succumbed, or were exposed way beforehand.
A key question here is how was Detective Sergeant Nick Bailey given a larger dose than other first responders. He was critically ill, but is now recovering. Does that mean he was heavily exposed at the bench, say from trying to resuscitate the pair? Or, as former police commissioner Ian Blair has suggested, did he go to their home after the bench? Was he looking for medicine for the pair in their house? We don't know. But it looks most likely that the pair were exposed at the start of their afternoon in Salisbury and they carried the contamination with them to all three places. This means the agent took hours to affect them.
Why did the presumed would-be assassin choose something so specific and traceable?
On Monday, Theresa May told Parliament that Skripal and his daughter were poisoned with Novichok, which is a Soviet-era poison made in the '70s to evade various chemical weapons treaties and provide a more stable, two-part agent that was harder to detect.
But was this ordered at the highest level in the Kremlin? That is in an important question, and there is no hard evidence of that right now. Such an allegation means that Vladimir Putin, less than two weeks ahead of an election (that he will undoubtedly win), had ordered a public killing of a dissident that could really only be traced back to Moscow.
It would risk more sanctions on Russia's beleaguered economy and greater isolation: two things that have not played well with an electorate he is careful to keep happy enough.
The other option is that it was done by a rogue part of the Russian state, set upon further isolating Moscow or seeking to please a Kremlin that wouldn't be brazen enough to order such an act itself. Or that someone -- criminal or private -- has this deadly agent who should not.
Either option is, of course, bad news, and suggest Moscow is out of control, with nerve agents being used with a reckless disregard for British public safety.
This is clearly one reason why London has given Moscow 24 hours to account for these chemical weapon stocks and agree to let UN inspectors in. They almost certainly won't agree to that embarrassment, days ahead of a key election. So we are left with a likely escalation on Wednesday.
Why are people in Salisbury suddenly being asked to wash all their clothes?
The official response from the UK has been puzzling. At first, they thought it might have been an opioid. Forty-eight hours later the counter terrorism police took the lead in the investigation. And then 24 hours after that they stepped forwards to say they knew the "specific nerve agent" it was. Yet, it was only 48 hours after that when the British army was sent in, providing pictures of soldiers in protective suits removing cars and securing gravestones.
If there was at no point any risk to public safety -- as health officials insisted from the start -- these images risked looking like they served a political purpose by making the threat seem severe and the military the required response.
And then finally, an entire week later, and four days after the agent has been identified, 500 locals who went to the pub or restaurant are told to wash their clothes and themselves.
It's a baffling chain of events and shows a government that either did not understand what it was dealing with for an entire week, despite insisting there was no threat to public health, or after seven days is amplifying the threat as the political ramifications rear their head.
This story has been updated to reflect the latest developments Monday.