Who knew what, when?
Often the simplest questions are the hardest to answer.
As we reported yesterday, the troubles of the inquiry into historical child abuse continue to unravel.
But the departure of the inquiry head, Dame Lowell Goddard, potentially could cause the prime minister herself a significant political headache.
During Prime Minister's Questions today Theresa May was asked the question - what did she know, and when, about the problems at the inquiry? The prime minister's answer implied that she had known something was up.
She said: "There were stories around about the inquiry and about individuals related to the inquiry but the home secretary cannot intervene on the basis of suspicion, rumour or hearsay."
A conversation in April involving a Home Office official "was asked to be confidential and as far I am aware it was treated as such", she said.
"I think it is important for us to recognise that when the Home Office was officially informed of issues, the Home Office acted."
It seemed that Theresa May all but admitted that she had been aware of problems in the spring but then nothing happened. That's already prompted accusations of a "cover-up" and demands for her to "come clean" on exactly what she knew.
Her officials this afternoon have just confirmed that she did know of "tensions" between the inquiry chair and members of the panel, "some weeks" before there was an official alert, at the end of July.
That confirmation begs more questions though, that Number 10 is not ready to answer. Who told Theresa May that there were problems afoot? And what precisely was she told? We don't know. And Downing Street won't say.
But her opponents are likely to point out that Theresa May heard of those "tensions" around the time that she was launching her bid to become PM.
The inquiry's problems could still end up at Number 10's door. That's because the troubled birth of this sensitive and politically charged investigation was under Theresa May's tenure at the Home Office where she was in charge for six years.
Her team point out that the independence of the inquiry had to be protected then, and must still be now. It is not for ministers, whether Theresa May at that point, or Amber Rudd now, to stick their noses in.
But just as politicians like to associate themselves with the success of projects they began, so too they struggle to dissociate themselves from their failure.
There is no suggestion at this stage that any minister, let alone Theresa May, was involved in trying to hide what was going on, but the prime minister may even be called by MPs who want to press her publicly on exactly what she did know.