It has been a headline story in Britain with many familiar themes - undercover policing, the infiltration of a protest movement, then a trial at which the nature of that covert activity becomes the issue and disclosure is sought.
We now read about investigations, inquiries and reviews of procedure and all the usual questions are asked about costs, necessity, operational responsibility and the issue of proportionality. In other words: do the tactics match the task? Can they be justified?
There are other questions about how long you leave an officer undercover and when does how long become too long.
Who has operational responsibility? Should decisions be left with the officer on the ground or made elsewhere - by someone detached from the situation?
Here, we have read and heard it all before, in different storylines, with different actors, but in plays that take police officers and members of the Security Service (MI5) into a dangerous double life.
It is about infiltration, intelligence-gathering, getting in close, watching and listening. And, then, there is the question about how close is too close.
I imagine that, during those years of stand-off and confrontation at the Orange march in Drumcree, undercover police officers will have mingled in the protests - there in the crowd as human listening devices.
Monday's Guardian headline shouted out: Clean-up of covert policing ordered after Mark Kennedy revelations.
Kennedy - a former undercover constable - had spent years in the role of an environmental activist.
Then, earlier this month, the trial of six men allegedly involved in a protest at a power station in Nottingham in 2009 was stopped after their defence team pressed for full disclosure of the officer's activities.
Those involved in that covert policing/security world - whether in Britain or here - don't like disclosure; scrutiny that shines a light on their secret tactics.
They have all kinds of terms to describe those undercover plays such as 'alternative means of entry' and 'substitution'.
These are two we know in the Northern Ireland context that apply to the world of counter- terrorism.
The first is about entering premises - the police and the Security Service letting themselves in when the owner is out to carry out a search, or place bugs.
The second - 'substitution' - is when explosives have been removed from bombs and replaced with another substance.
One such example was the dissident republican attack on the police training college at Garnerville in east Belfast in 2002. It looked like an attack, sounded like a bomb, but those working in that undercover world know it wasn't.
And that is how close and how dangerous it is - using an informer to get information about the bomb and then an expert disarming it before it is transported and placed at its target.
The role of the undercover officer is to step into all sorts of people's lives and circumstances; to be close enough to see and hear their target, but not that obvious that the target sees them for who they really are - rather than who they are pretending to be.
There was an example of this in the so-called 'Stormontgate' case here - an investigation into alleged IRA intelligence-gathering at the heart of government.
A house where documents were hidden was at the centre of a surveillance operation. The Special Branch and MI5 knew everything about the inside of the house.
They knew everything about the documents hidden there. Indeed, as part of alternative means of entry, they removed the papers, photocopied them and put them back.
The owner of the house - a sportsman - had company when he trained and travelled. And that is how close it gets: some call it 'babysitting'.
The undercover officers know you, but you don't know them. It is a cat-and-mouse play, using all kinds of gadgetry and tactics.
In all the fuss and fallout from the Mark Kennedy case, we read how he described undercover policing as "grey and murky".
It has to be. It can't be obvious. It is not meant to be seen. And it requires police officers and members of the Security Service to live those double lives.
Some years ago, I had an arrangement to meet an MI5 officer in my hometown. When I arrived he was waiting outside and asked if we could go somewhere else.
He explained that there was someone inside who knew him, but who didn't really know him; knew him as something other than an MI5 officer.
And he was worried that that person seeing him in the company of a journalist might begin to ask questions that he could not answer.
There will always be questions about undercover activity. And there will always be investigations and inquiries about how and why it is done.
Former PSNI Chief Constable Sir Hugh Orde - now president of the Association of Chief Police Officers (ACPO) - is part of the different reviews now happening.
"We have been trying to put these very important national units into a more transparent and accountable structure," he told the Belfast Telegraph.
"We have been working on this for over a year.
"On three occasions, I have given evidence to a [House of Commons] select committee raising these concerns at the lack of any national infrastructure to take these units on."
Whatever happens, undercover policing/covert operations will always be grey and murky: they can't be black and white.