With an hour to go before kick-off on a lovely soft spring day, the Cardiff City Stadium is still a low-fi kind of place. Cardiff need to win their final home game against Crystal Palace to have any hope of extending their stay in the world’s richest league beyond a single, spirited season. But there is, if anything, an absence of tension in the air.

The Cardiff fans stroll in familial groups around the concrete walkways of this handsome, out-of-town retail park of a stadium. From the stands the pitch is half in sunshine, shadowed now and then by fluffy coastal clouds.

The live TV crew on the touchline chatter around their lighted table, willing some urgency into the day. In front of a vaguely curious pre-match crowd Martin Keown rasps his lines about doing well to survive this long and just lacking a bit in front of goal, speaking as ever with the lapel-grabbing urgency of a morally compromised chief inspector giving his maverick DI one last chance or he’s off the force.

This, the broadcasters have agreed, is the story of Cardiff’s season: resilience in the face of likely relegation; and admiration for the way under Neil Warnock they have managed to “take it this far”.

Except, of course, this isn’t quite right. No one wants to talk about it. But the biggest story in Cardiff, and indeed the single most startling event of the season in English football, is something so tangled and strange it is still hard to look it square in the eye.

The desecration of Emiliano Sala by English football has continued in the last weeks. It is now nearly four months since Sala was killed in a plane crash south of Jersey. He was flying to Cardiff on a single-engine Piper Malibu hired by the intermediary Willie McKay and his son, Mark, to take up a move to the Premier League he had initially resisted.

It is a death that continues to burn with its own dark light. At the end of April Sala’s father, Horacio, died of heart problems aged 58. Friends say he never recovered from the shock.

Things keep unravelling. How far can we get with this? A few days before the Palace game pictures had appeared on UK social media of Sala’s corpse. The suggestion is thieves had broken into the morgue where his body was being kept.

By the time the Palace game comes around the Cardiff fans’ shrine to Sala has been cleared away, the flowers and flags removed from the statue of Fred Keenor. No one seems to know why. It was a touching thing, created by and for the same fans who have reacted with grace and warmth.

Emiliano Sala flourished at Nantes, attracting Cardiff’s interest as they sought a forward to help them avoid relegation. Photograph: Stéphane Mahé/Reuters

But then questions of belonging and ownership have become a genuine issue in the last few weeks. Nantes are currently progressing their formal request to Fifa for full payment of Sala’s transfer fee. They maintain, understandably, he was a Cardiff player when he died.

Sala was born in Santa Fe, Lionel Messi’s home state. He became a professional footballer at Bordeaux. He became a player of substance at Nantes. He became Cardiff’s record signing in January. And now he has become this. Free on board. Free at origin. In death Sala has become a shipping dispute.

To look into this is to be machine-gunned with toxic details. Here’s another one. Cardiff’s lawyers call their files on the wrangle with Nantes “The Onion”. It’s a gallows-humour joke. There is so much information here, so many interested parties, so many layers. Plus of course the more you peel it, the more it stinks. Zoom in a little and the Sala affair is a story of wrong turns, bad calls, bad luck. But it also spreads itself wider, digging a finger into so many corners of this darkly baroque industry: from a wild-west transfer system, to the shark-pool of interests and middlemen, to the basic commodification of the human product.

We are all in this to some degree. From the money-lust culture of the English Premier League to the startling way the story itself was covered at the time in rolling news media, as though this search for a body was just another development in a breaking transfer story, another detail of the club medical, a dramatic change of heart from the in-demand Ligue 1 forward.

Blame has hovered like a mist without ever quite touching anyone. Nobody did this exactly. Nobody is responsible. But there are shades of grey, odd practices, sharp edges. At times football looks like something bound in mud and fog, a place where things get lost, where it is just accepted that if the world goes wrong, it was, in some off-hand manner, never meant to go right.

Later in the day Warnock will speak well about Sala’s absence, but not until he has also described a season that pivoted around his brutal and untimely death as “the best I’ve ever had in management”.

Warnock has seemed genuinely moved through all this, has handled his public duties with tact. But in the post-relegation debrief Sala’s death is couched in the same terms you might use to describe an untimely injury to a key squad member.

“We have missed a striker. Someone asked me about Emiliano … we spent two months trying to get a player,” Warnock shrugs. “I wish we would have had Emiliano with us. I think he’d have scored 10 goals, you saw the chances we had out there today.”

Neil Warnock with his Cardiff players after relegation is confirmed, a jerry-built top-flight team playing at the edge of their capacities. Photograph: Geoff Caddick/AFP/Getty Images

The game has a sleepy opening. Cardiff start on the attack. A few minutes in Víctor Camarasa pulls up injured and is applauded warmly as he limps off. Camarasa, on loan from Real Betis, has been a fine player for Cardiff. This could be the last they see of him.

Aron Gunnarsson is also playing his last game after eight years at the club, already engaged to join Heimir Hallgrímsson’s Al-Arabi in Qatar. Cardiff have been a vigorous, jerry-built Premier League team. These players have been operating at the edge of their capacities.

Midway through the first half the home crowd rouses itself to boo their former loanee Wilfried Zaha as he snipes inside and shoots wide. Two minutes later Zaha responds by scoring the goal that might just send them down, jinking left, then right, before shooting low into the corner.

Cardiff equalise shortly after, but Palace’s front four look irresistible. With 40 minutes gone Michy Batshuayi finds the space to spank a shot into the top corner. The goal seems to draw a shared sigh around the stands as Cardiff’s supporters head for the aisles at half-time.

The best response would have been for the clubs to get together and talk, split the costs a little, look after the family

More detail on the Sala case has emerged in the last few weeks. A preliminary Air Accidents Investigation Branch report has been published, to be followed by a longer one, perhaps as late as next year. Its chief effect is to bring into focus the terror of those final moments.

“Anyway guys, I’m up in this plane that feels like it’s falling to pieces, and I’m going to Cardiff,” Sala told a group of friends on WhatsApp as he took his seat. The sun had set in Nantes at 5.50pm. Sala went through security 40 minutes later and took his seat with the pilot David Ibbotson. They took off as scheduled at 7.15, Ibbotson navigating via an app on his tablet. The Piper Malibu cruised at 6,000ft. Thirteen miles south of Guernsey Ibbotson descended to just over 5,000, telling air traffic controllers “just avoided a patch there”. The journey was run under visual flight rules: or in other words keep your eyes open and don’t fly through clouds.

The last radio contact came at 8.12pm. And three minutes later the flight became a nightmare. The Malibu dropped from 3,900ft to 1,600ft in 20 seconds while veering wildly to the right. It climbed rapidly again. Then: blackout.

The remains of the plane were found two weeks later below this last recorded location. It had been torn about by the plunge straight down. Most of the wings and the tail were gone. Sala died from head and chest injuries. The AAIB report says his corpse was “held in place by the wreckage”. To this day Ibbotson’s body is still out there. Full fathom five he lies. Vale, Mr Ibbotson and rest in peace.

Back on land the news of Sala’s disappearance seemed to have reached Cardiff straight away. The club had a player liaison officer waiting at the airport. The plane didn’t arrive. Warnock was notified. He called McKay.

Here’s a good question: why was McKay involved in this at all? Not that it should be a surprise. At least five intermediaries are due a cut from this deal. And McKay is in his own way a frontiersman, present at the first rush of money into the Premier League in the early 1990s.

Bankruptcy in 2015 disqualified him from registering as an agent, and the Football Association seems to have decided McKay was acting for Nantes and is not in its jurisdiction. McKay says he was helping his son Mark “get to the top”. Why get registered, he has asked, when his son is? The McKays stand to make £1.5m from Nantes over the deal.

It is McKay’s email to Sala, released to L’Équipe in an attempt to exonerate himself, that should perhaps be preserved as a historic document, a snapshot of an industry. It is unintentionally chilling. McKay keeps on telling Sala the truth.

“Emiliano, My name is Willie McKay …. We are not interested in looking after your personal interests.” A good time, you’d think, to stop reading. McKay tells Sala that agents such as himself “only care about money” and encourages the player to cut his current agent Meïssa N’Diaye out of any deal, while dangling a £1m payment to Sala’s mother under his nose.

He admits to misleading the media about transfer interest from West Ham and Everton. In a horrible little touch he seems obsessed with planes generally: “We take our plane get clubs in it ... they will fly you over in their jet ... Cardiff can have a jet for you tonight or tomorrow.”

Willie McKay’s leaked email to L’Equipe revealed much about the way his industry works. Photograph: Nick Potts/PA

McKay’s method, self-described here, is pretty clear: identify a form player and acquire permission to hawk them around until he gets a bite; all the while putting rumours about to make that more likely, then trying to cut the players’ actual agent out of the picture.

The worst thing about this is that it is possibly half-true. This is how McKay makes his business work. Premier League clubs at a certain level really are that understocked with specialist knowledge. And yet there are holes in what McKay did here. At the very least the plane is on the McKays. They hired and paid for it. There is still a note of uncertainty around its real ownership, but it was well-serviced. The licensing status of the plane to carry commercial flights – with all its added regulations – has been questioned. What is certain is that Ibbotson was a stand-in for a regular pilot, Dave Henderson. It has been suggested Ibbotson was colour-blind, and thus not qualified to fly at night, although this is also unconfirmed. One thing is certain. Flying wasn’t Ibbotson’s main job. The man flying Sala to Cardiff was also a gas engineer.

What next then? Cardiff received the first formal demand for Sala’s transfer fee on 6 February, the same day Sala’s body was identified by Dorset police. Cardiff are stalling on paying, asking questions to do with the flight, to do with third-party ownership. It seems strange. Presumably some legal advice has told them this is a possible escape route from liability. But why turn this into a saga?

The best response to all this would have been for the clubs to simply get together and talk, split the costs a little, look after the family, staunch the bleeding. It is Vincent Tan who will now drive how it plays out in practice. And Cardiff’s owner is the hardest of hard-nosed operators. Sala has been buried. His inquest will return at some stage later this year. But some part of him is still out there, suspended between two places.

Back at the Cardiff City Stadium Warnock spends large parts of the second half angrily bearding the fourth official, Graham Scott. Scott shrugs and looks nonplussed each time Warnock comes marching over in his blue padded tracksuit, the neighbour from hell with another gripe about tennis balls over the fence.

Andros Townsend scores Palace’s third, after a powerful right-angled dribble from halfway. “City till I die,” the Cardiff fans sing in response. Several rounds of “One Neil Warnock” follow as the game winds down. It is a nice moment, possibly even Warnock’s own farewell. Again no one really knows for sure. The final whistle brings a warm round of shared applause, and an ambling lap of the pitch from the Cardiff squad. Relegation is not a surprise but it still hurts.

Outside the walkways are empty two hours after the final whistle, with the feeling of a stadium already turning toward its summer hibernation. Something has changed though. The Fred Keenor statue has an addition. Someone has left a small damp bunch of flowers on its highest ledge. Gone, but remembered by the right people: Sala’s story is one that has, you feel, still got plenty of distance left to run.

• This article was amended on 17 May 2019. An earlier version incorrectly described the crashed plane as a “Piper Alpha”. It was a Piper Malibu.