Hi, it's Dad. Firstly, don't worry, I know I normally email, but as you know I'm in hospital and the connection here is non-existent.

Secondly, I'm fine. Broken leg is not a big deal. I can even hobble enough to go post this later. No, the real reason for the letter, other than the fact that daytime TV is so terrible, is that, being in hospital again, for only the second time in my life, has brought back something that happened the first time.

Now, bear with me, cos some of this you already know, but there are bits you don't.

Do you remember all those years ago when you were three or four and you stuck the tail of a toy dinosaur up my nose, and I ended up in hospital for three days with cellulitis? Of course you do, cos we've joshed you about it loads of times. Well, there was another part to that story which you were not told.

The way it went was this:

When I was in hospital the last time, a man died in the bed opposite me. I was in the second bed on the left in an eight bed ward, and he was in the last on the right - bed five. He was just an average guy, from what I could see, though he was quite heavily sedated due to being pretty ill with some infection or other. He was ranting a bit, and his mind was wandering all over, talking about milk bottles one minute and the aliens amongst us the next, but most of it was too quiet to hear, and he was muttering under his breath on and off most of the evening, with the occasional outburst of gibberish. The nurses were in every two hours checking his pulse and so forth.

I was getting large injections of antibiotics at six hour intervals, and I was due one at midnight, so even though I was tired and my eyes were heavy, I was trying to stay awake - it's not nice to wake up with a nurse pushing ice cold fluid straight out of the fridge into the back of your hand.

The ward was semi-dark, the way hospitals are at night, and I half surfaced, and saw this doctor cross the room to check on the guy in bed five. A few seconds later, the nurse came in with my medication, and she nodded briefly in the doctor's direction, and came across to me. The doctor left, and that was that.

Two hours later I was woken by a fuss around bed five. The curtains had been pulled and there was a lot of quiet talk. They drew the curtains around my bed when they realised that I was awake, and the next morning, bed five was empty. He had 'passed away' in the night.

This was a bit creepy, but I didn't give it a lot of thought until the police called a few days later. You never got to see any of this, cos we kept you out of the way. Apparently the man had died of some kind of over-medication, and they were looking into the situation, and could I remember anything about that night? My first question was when did he die, and as they seemed to think it was pretty much around midnight, my next thought was the doctor that had been checking on him. I had noticed him fiddling with the equipment, but that's what doctors do, isn't it? I mentioned him, and they were interested, but I told them I actually hadn't looked at the doctor's face, so it wasn't much help.

The story made a small item in the papers, but it seemed that no-one knew which doctor had been there that night, and it just went away.

Now, as it happens, I haven't even told your mother this part, as, well, you know she spends quite a lot of time in hospitals, so I didn't want to creep her out. So whatever you do, do not tell your mother, OK?

What I didn't tell anyone was that I had noticed three things about the doctor which were odd. In fact, the reason I didn't tell the police initially was that I thought they were so odd that if they didn't think that I was out of my skull of fever or whatever, they would think that I was a nut.

The first was that he made no noise. That sounds kind of stupid, as you don't expect a doctor on a ward at night to stamp around, but he was wearing the same rubbery soled shoes that most of the medical people were wearing, and they had been squeaking across the lino floor all day. I had noticed it particularly, as I had nothing else to do, and it had amused me at first, and irritated me later.

The second was odder, and I noticed it because he didn't squeak, so I had paid attention to his feet.

There had been a bit of a mess made a short time earlier, when one of the junior nurses had gone to use the sterilising gel at the door and had found it empty. Now, these guys were rigid on the hand washing thing, so she went and got a new bottle, and it slipped from her hand or something, and next thing there is a strong smell of alcohol and they are mopping the mess up. Anyway, the end result was a poorly cleaned up wet patch on the floor inside the door with a couple of warning signs next to it. The nurse coming with my medication walked through it, and for several steps, she left prints on the floor. Then she started to squeak again.

The doctor did neither. He did not squeak. He did not leave footprints either.

Both of these things I had noticed at the time, but there was a third thing which I really only noticed when the police came to ask me about the incident; I had looked at the doctor's feet, his hands, his body, and obviously, enough to recognise him as being a doctor, but I had never actually looked at his face.

I'm not good with faces, so I have to try hard to recall them, but when the police asked me what the guy looked like, I had nothing to tell them. Nothing at all. I had never looked, even once, even though for a couple of minutes, he was the only moving thing in the room.

This I found odd. On reflection, I came to think that the nurse had never actually looked at him either. She nodded in his general direction, but had immediately turned to me.

Now, I have been lucky enough not to go into hospital myself since then, but what with you and your brother, and your mother's health, I have spent a lot of time sitting in waiting rooms, and I will tell you another weird thing: there are more than one of the men with the silent feet.

Actually, they are not all men. Some are women. Look the next time you are in a hospital. There are staff moving around that have no patients, they make no noise, no-one talks to them, and they talk to no-one. They are just there. They pick up clipboards, and push things around on trolleys, and seem to fit in, but they are all but invisible. There are even people who are not staff. There are some people that you see in waiting rooms that no-one calls to be seen, but yet no-one asks what they are doing there.

If you try to look directly at them, you will have an almost overwhelming urge to look anywhere else. Oh, and they tend to avoid walking on wet surfaces.

I have only once seen someone that I think was the same as whatever these people are anywhere other than a hospital. It was at the scene of a road accident that I was passing. In the middle of a bustle of people at the accident, there was one man standing still as everyone else walked around him. I couldn't tell if he had silent feet, but I found my glance sliding off him immediately.

My theory is that they are not generally harmful. Whether the one I saw that night was helping the man in bed five, or killing him, I don't know. Was this related to his ramblings about aliens, or even milk bottles, I don't know. All I know is that they like to hang around places where people die.

Actually, to be honest, not all of the above is not strictly true. I wasn't going to say this, but I think I need to get it off my chest, even if you think I must have been seeing things.

There was one brief moment when I found myself looking at that first doctor's face.

I do not like needles, as you know, and so I had to force myself to look elsewhere as the nurse put the needle in the line in my hand. I needed desperately to look somewhere other than at her, and the doctor was just leaving the room. For a second he was framed in the doorway, and the light from the corridor fell full on his face. I had this weird feeling that I didn't want to look in his direction, yet my need to look at something other than the needle was overwhelming, and I looked, for maybe a second, and then I found myself staring at the fire extinguisher in the corridor outside, knowing that he was looking at me, until he walked away and the door closed.

What I saw shook me, I must admit. For a long time, I didn't want to think about it, but what I saw, when I looked at the doctor's face, was the face of the man in bed five. The face of the man that I later found out had just died.

What is more important, and what has stimulated me to write this to you, is that I have two doctors here. One is a small, rotund, Polish doctor with whom I have conversations that mainly consist of us asking the other to repeat themselves.

The other doctor's face I have never had the urge to look at.

See you soon,