Felix and I were given a room to ourselves on the fifth floor, the level of the maternity wing reserved for sick babies and their mothers.

I didn’t panic. Actually, I felt like a fraud. I was sure that before long the mystery would be solved and the jaundice would clear, and we’d be home again and preparing for Felix’s first Christmas.

They treated the jaundice. Correction: I treated the jaundice. Me and the sun. Felix needed milk and plenty of it. They weighed his nappies to check he was taking in enough of it, and he was. Mark went home to relieve his mother and make sure the girls were all right, and Felix and I were alone together.

It was a beautiful day. The sun coming into our room was very bright, and Felix lay in the sunshine after his feed and snoozed. He looked so peaceful, and his skin was turning pink, losing that sickly hint of yellow. I pored over him when I should have been sleeping myself. He looked a bit like Ava and a bit like Mark, and also, a bit like me. But most of all he looked like his own perfect, new-minted self.

I was sure he’d be well enough to be discharged soon. But they did another blood test and the infection was still there.

He had a cannula inserted into his tiny hand, and a line pumping antibiotics into him, and it persisted.

People came and went, checking his temperature, administering his dosage. Mark visited with Ellie and Ava, bringing grapes and flowers. We had a short stretch of uninterrupted time together, the five of us: a birthday party, of sorts, around my hospital bed. The girls held Felix again. I could tell they were all worried, and trying more or less successfully not to show it.

In a way, it was a relief when they had gone again, and I could just concentrate on Felix.

His second night of life went by in the hospital cot, with a succession of people slipping in and out of the room in the darkness to monitor him. The next morning someone decided a urine sample was needed. Well, that was a joke. I ended up sitting round with one of the midwives, watching Felix lying in his cot with his nappy off, waiting for him to wee, then missing the moment when he did. In the end one of the midwives came up with the idea of putting cotton wool inside his nappy and using a pipette to get the sample out of it. I congratulated her as if we’d cracked it. As if everything else would be easy now the problem of how to carry out the necessary test had been solved.

Soon Felix would be in the clear, and we would be free to go home.

But within the hour the test became unnecessary, and we were overtaken by events.

A paediatrician came to carry out a full body inspection, and saw what nobody else had: the cause of the infection. A twisted testicle, red and slightly swollen. When the blood supply to part of the body is cut off, it dies. And the body of a living person cannot accommodate a part of the body that is already dead.