The butterfly effect. A goalkeeper flaps his hands in Abidjan, Ivory Coast, and there is an earthquake in Bilbao, Spain. In Barcelona too, and well beyond.

With just a few seconds left in their final group game at the Africa Cup of Nations and the ball heading harmlessly out of play, Ghana goalkeeper Richard Ofori, who had to do only one thing and that one thing was nothing, instead reached out a hand, tried to catch what he didn't need to catch and gave away the corner from which Mozambique scored. From 2-0 up in added time, Ghana were now level, on the edge of elimination. The error was as inexplicable as it was destructive. It was also the end.

But then, as Maria Arthuer says: when a window closes, a door opens. Arthuer is striker Iñaki Williams' mum, and she is wise.

Without that mistake, that moment of madness, a tiny fraction of a second, the slightest of touches, Ghana would still be in the African Cup of Nations and FC Barcelona might still be in the Copa del Rey. Without that moment, Barcelona manager Xavi Hernandez might not have announced he was walking away. Without that moment, there might be no Copa del Rey semifinal between Atletico Madrid and the club that founded them (stream LIVE on Wednesday at 3:30 p.m. ET on ESPN+), no chance of a second-ever Basque derby final -- this time with fans, having previously been denied that by the pandemic, despite waiting an entire year to play, 2020's final eventually going ahead in 2021. Without it, Athletic Club wouldn't have lived the day of their lives.

Williams certainly wouldn't. "Incredible," he called it, "totally mad, a story with a happy ending."

Just how happy will be defined over the next month, when Athletic face Atletico in the Copa del Rey semifinal, and maybe on April 6 in Seville, the day of the final. Whatever happens, though, they will always have this.

"You lose a lot in football, a hell of a lot," Athletic coach Ernesto Valverde said, and his team still might. "But one day, when fans look back on the good moments, this will be one of them. They will remember this -- and with a smile."

Ofori's mistake was on Jan. 22. Ghana had given away a penalty in the 91st minute and a corner in the 94th and were virtually out. Virtually, but not quite. The following day, the Ghana players sat and watched from the physio room as Cameroon played Gambia, their fate in someone else's hands. Williams' fate, especially. They didn't have much hope but then, unexpectedly, hope was handed to them: a wonderful, wild match, the best anyone could remember, saw Gambia lead with three minutes left; Ghana might have made it through after all, rescued. Only then Cameron scored twice, in the 87th and 91st minutes. That was Jan. 23, in the Ivory Coast. It was over.

For Williams, it had just begun.

On Jan. 24, he was back in Bilbao, scoring the third goal in a 4-2 extra-time win, knocking Barcelona out the cup and sending Athletic through. He had been in the country less than 12 hours.

"It was written," Valverde said. Four days later, Xavi -- who had linked his future as Barcelona coach to winning titles and had just lost the only one he could realistically win -- announced that he was leaving the club in the summer.

Next week, Athletic play the Copa del Rey semifinal against Atletico. It is their fifth semifinal in a row. No one treats this trophy like they do. Here was the proof: looking down the lens of the TV camera at full time, Williams shouted, "I came for a reason."

He came for this, no distance stopping him. "Not in my wildest dreams would I have imagined this, being here today. I still can't believe I am," he said, when at last it was over. "These have been 24 frenetic hours."

Chaos, he called it. But he had been determined to get back for the semifinal. The Africa Cup Nations had been frustrating -- just one start in three games -- and he had missed five games for Athletic by being away. Ghana was out now and that hurt; he didn't want to miss any more games back home. And it is home, the best place to heal. And so that's where he was heading, and in a hurry.

"We sat and watched Cameroon," Williams explained later. "If the ball goes in or not, if there's a handball in the last minute, if they come back ... when Cameroon won, we rushed to get the tickets."

And so it began. Pack your case, get on the road, the clock ticking. "From the moment we knew we had been knocked out, everyone was all-in on helping me get back," Williams said -- scrambling to bring their boy home. His dad picked him up and drove him to the airport. A midnight flight, through the darkness -- asleep almost all the way -- a 6:45 arrival in Paris the next morning, the day of the game. A car across the city, another flight, another airport, no time for the duty free shop, not even to buy a giant Toblerone. Then 45 minutes of Paris traffic, of nerves, from Charles de Gaulle to Le Bourget, a private plane waiting. It cost 6,000; the best 6,000 Athletic ever spent.

Back in Bilbao, in the team hotel, Valverde was pacing. "I was asking how it had gone, had he arrived yet? Was he going to make it or not?" he said. On Flightradar24, Williams' plane from Paris was being followed by thousands of Athletic fans.

"It was like they were pushing it home," Valverde smiled later. "I didn't anticipate so much expectation," Williams said, having watched it unfold on social media. A bit before 1 p.m., 13 hours, two flights, four airports, three car journeys, 3,700 miles and not enough sleep later, he did.

"I'm here to win," Williams said.

AMBIENTAZO in Bilbao. Athletic fans waiting to welcome the team to San Mamés for a big #CopaDelRey tie against Barça. @sidlowe pic.twitter.com/cqCjhGfaNL

The Spanish Football Podcast (@tsf_podcast) January 24, 2024

There was one more journey to make: on a bus through the fans and the fireworks to San Mames, thousands and thousands of people lining the route, hammering at the side as it passed. It was going to be a great night and Williams insisted: "Even if it was just to watch my teammates, I was determined to be there."

Yet it wasn't just to watch: he wasn't really in a fit state to play, he hadn't slept the way an athlete is supposed to and he was exhausted, but he was going to play. Oh, he was going to play.

"Once he arrived, I knew," Valverde said. "He wasn't going to start but I was clear he would play. He was going to have to wait until the second half but he was going to be an emotional boost for us because of what Iñaki means, not just on the pitch, in the group, for the fans too. That was a weapon we had to use."

When he ran on, with the score 2-2 and 50,953 people there, the roar could be heard back in Abidjan. When he scored to make it 3-2, hitting the post and then following up his own rebound to put Athletic one foot into the semifinal, the place could have collapsed. He ran to the corner, everyone going wild. Welcome home. That was minute 106 and Athletic led. The fourth followed on 120. The scorer? Iñaki's little brother, Nico Williams.

"If this is a dream, don't wake me up!" Iñaki tweeted later. He had been in the Ivory Coast, in France and in Spain in 24 hours. Now he was in the semifinal of the cup. From the Cup of Nations to the Copa del Rey, 48 hours apart. He had been in the country less than 12 hours.

"He's a phenomenon," centre-back Dani Vivian said.

"From sadness to happiness there is just a step," Williams said.

A step, and some journey. "My mum said to me yesterday that when a window closes a door opens and that's the way it was," Williams said. "It was sad for all of us with the national team to be knocked out. There was the uncertainty, not knowing what was going to happen but once we knew that we were out, my head was set upon being here with my teammates and helping any way could. One of the fears I had was going to the Cup of Nations and knowing that I would feel responsible if things then didn't go so well for Athletic. That weighed on me. But the team has responded well, my teammates have played well, which is lovely, and it is lovely to be here.

"It was hard to be here but I wanted to be here. We have now reached five semifinals in a row: we're an ambitious team. Now we have to put the icing on the cake: we have to go and play the final with fans, which is what we dream of, what we all want. I have experienced that once before and I want all those that haven't to be able to live it too. Hopefully then we can round off a magnificent season, add that finishing touch in gold. Quietly, under the radar, work day by day. This is huge: in the cup, against Barcelona. Just the finishing touch is left," Williams added.

Whatever happens next, he said, it had been the perfect day. It was midnight, and it was almost over. "This is for everyone to enjoy tonight," Williams said. Well, almost everyone.

"It's been mad and I'm shattered," he said sitting there, rubbing his eyes, head lolling, struggling to stay awake, everything catching up with him at last as the adrenaline subsided. "I would love to go and have a couple of beers with my teammates but I'm exhausted. I'm going home. I'm going to bed, happy."