The distance runner who delivered a telling one-two to win 5000m and 10,000m gold at the 2012 London Olympics and then did so again at the World Championships in Moscow last summer, arrived to join the British team on the eve of the European Athletics Championships, which start in the Letzigrund Stadium in Zurich today, explaining that a knockout blow was the reason behind his absence from the Commonwealth Games.
The 31-year-old had withdrawn from the England team for the 5000m and 10,000m at Glasgow 2014, citing a lack of fitness after suffering from illness in the wake of his disappointing eighth-placed finish on his marathon debut in London in April. The full story was revealed when Farah arrived at the British team hotel, in readiness for the 10,000m final tomorrow evening.
"I basically had a tooth taken out because it was chipped and it got infected," he said. "I was in a bit of pain, but went for a run, and when I came back I literally collapsed on the bathroom floor, completely knocked out. I had my phone in my pocket, so when I woke up and became conscious I called Cam Levins, my training partner - the Canadian guy who came third in the 10,000m at the Commonwealth Games - and he came round and got me on to my bed.
"I was in so much pain from my stomach, and so he called an ambulance and it took me to hospital. I then had to be airlifted to the main hospital as they thought something was going on with my heart. It was just crazy. I was in hospital for four days and it was scary, but these things happen.
"I missed quite a lot of running. I would have loved to have come back and continued the road to the Commonwealth Games. I didn't want to disappoint my fans and all those who had bought tickets, but I just wasn't ready. I was nowhere near ready."
The critical point, after Farah had been checked out by the medical staff at British Athletics and passed fit to resume running, came when he was training on the track at his European high altitude base at Font Romeu in the French Pyrenees. "I was doing a track session and Paula Radcliffe was timing me and she told me I should stop," he recounted. "When someone like Paula tells you to stop, you know there is something wrong. I just wasn't right. She could see that. It took a lot out of me.
"Later on, Paula said I'd taken the easy option [in withdrawing from the Commonwealth Games], which is not fair as she'd seen me struggle. I was quite disappointed, but in myself, Mo Farah, if I'm going to turn up I have to be 100%. I'm not going to turn up in my home country and get beaten. A lot of those Kenyan guys I can beat when I'm 100%, but if I'm 80% or 90% I'm just asking to get beaten.
"For all the people who bought tickets, I am genuinely disappointed I couldn't take part. But I'd been through a lot. I just wasn't ready. I've done a lot of training since then. I'm two weeks further on, and I'm in decent shape now."
The incentive for Farah when he hits the comeback trail here tomorrow will be a place in the record books. He has already won four European outdoor medals in individual events - two golds at 5000m, one gold at 10,000m and a silver at 5000m - and no male athlete has ever won five, discounting relays.
The truth is, the double Olympic and world champion would not need to be at his best to win a European gold, let alone silver or bronze, such is the gap between himself and the rest of the continent.
"Those couple of weeks in Font Romeu, getting my head down, have really helped me," insisted Farah. "This year I need to do something.
"I didn't see much of the Commonwealth Games. It was painful because I really wanted to be there. It was hard to watch it."
Still, at least the man with the Midas touch has made it to Zurich - to add a little momentum to the push for British success on the European front.
Past instances of European Championships coming hard on the heels of Commonwealth Games on home ground have shown how hard it is for Scottish, English, Welsh and Northern Irish athletes to raise their game a second time.
Only two British winners at the 2002 Commonwealth Games in Manchester finished on top of the continental pile in Munich a fortnight later: javelin thrower Steve Backley and triple jumper Ashia Hansen.
Happily, from a Scottish perspective, Lee McConnell took silver in the 400m in Manchester and bronze in Munich.
It was a similar story in 1986. Only Roger Black (400m) and Steve Cram (1500m) struck individual gold at the Commonwealth Games in Edinburgh and at the European Championships in Stuttgart. One Scot took 4 x 100m relay medals in both: Elliot Bunney.
Cameron Sharp, father of Lynsey, was also a member of the medal-winning Scotland 4 x 100m team at Meadwobank - a happy omen for the Caledonian class of 2014, perhaps.