Agonised screams ricocheted off the grey metal walls. Hopeless and bewildered, Helen cuddled her newborn son. His tiny mouth opened like a great red tunnel, and his knees jerked up to his belly in spasms.

"Hush, Ricky. Don't cry. Mummy's here. Mummy loves you."

The volume was astonishing. How could anyone so tiny produce so much noise? His face was bright red, and screwed up with effort.

His howls drowned out her meaningless endearments. Tears pooled in her eyes, then floated away to form a cloud round her face. Helen sniffled. She'd had a wild final night in port, and obviously she'd imagined the contraceptives. Now she was alone with Ricky, most of the way to Jupiter.

Dammit, when would the Compudoc tell her what was wrong with him? She'd had it download data on childbirth and babies as soon as she'd managed to believe she really was pregnant.

The computer beeped. She couldn't read the display for tears.

"Vocal," she commanded.

"DIAGNOSIS: Infant colic. Probability, 98 per cent"

Colic? Didn't horses die of that? "Give detail on colic."

"Baby swallows air or small intestine produces methane. Zero-G aggravates the condition, because the air is not at the top of the stomach and therefore the patient is unable to burp. Infant abdominal muscles too weak to expel gases. Build up is uncomfortable, but causes no long term damage."

Was that all? She had thought Ricky was dying. She floated with her mouth open for several minutes, and then the shakes started. Ricky would live.

The relief lasted ten minutes. Then the crying started to set her teeth on edge.

"Give detail on treatment."

"Medicines of limited effectiveness exist, but there are none available on this ship."

The screams continued. Poor Ricky, it wasn't his fault, but oh how she missed silence! Deep space loneliness had worn away at her nerves, until she'd actually looked forward to the sound of a crying baby to keep her company.

The bawling of a healthy, hungry baby was one thing. This was quite another. Now she knew why writers called screams "piercing". These went through her skull like a laser blast. She kissed Ricky's head and rocked him from side to side, crooning, "Hush now darling, don't you cry. Mama's gonna sing you a lullaby."

She could scarcely hear herself think, never mind sing.

Her old self-doubt began whispering at her. She'd been desperate to be a perfect mother, but it would be just like her to screw up, to forget the obvious. Sometimes it seemed her whole childhood had consisted of her own mother clucking her tongue, rolling her eyes to the ceiling and saying, "Oh Helen!" She remembered a long succession of lost mittens, forgotten keys, missed buses and mediocre exam results. One year her school report was eight A's and one B. Mum had said, "So what went wrong in geography?"

Three hours later, Ricky was still screaming, and Helen was crying again. She couldn't bear this noise! A million years of evolution had programmed her to jump to his every whimper. Now he howled, bent double in obvious pain, and she could do nothing at all about it. Helen felt like a laboratory dog, chained down on an electrified floor.

Ricky screamed on. And on. And on.

Helen knew she was useless to Ricky. All she could give him were cuddles, which were about as much use as spitting on a forest fire.

Helen jiggled Ricky up and down, and murmured rubbish though a haze of weariness.

She was so tired. The noise itself was exhausting, and she'd given birth only two days ago. Her body screamed for sleep, and Ricky kept on screaming. Helen began to get a hazy feeling of déjà vu. Somewhere she had tried to comfort a screaming baby before. Or was it just that she'd been doing this for hours?

"All right! I'm doing the best I can, sweetheart. I'm trying for God's sake!"

She massaged his stomach, bounced around the room with him, swung him to and fro, and sang every nursery rhyme she could think of until she was hoarse. It made no difference that she could see. Was Ricky just acting? But no, he was only two days old, how could he know what manipulation was?

Oh Helen! Can't you do anything right?

Helen sucked her thumb, watching wide-eyed as Mum rocked a screaming baby. Mum was crying too.

Where had that come from? It was like a few seconds of video spliced into reality. It felt like a memory, but she'd never had any brothers or sisters. She couldn't remember Mum ever babysitting either. It must be her imagination.

As soon as they got to Jupiter, she'd get Ricky adopted. It would be a terrible wrench to give him up, but it wasn't fair to keep him. He needed a competent mother, not her. The decision made her feel better for a while, replacing shame and panic with simple grief.

How much longer would this go on? Presumably Ricky would sleep from exhaustion eventually.

Helen's Mum screamed, "Stop being such a baby! I can't stand it!"

But the baby screamed on, jerking his tiny legs to his belly.

It was so hard to think, between noise, exhaustion and self-doubt. If only she had some earplugs! Her emotions swung wildly. First she'd pity Ricky. Then she'd pity herself. Nobody could cope with this indefinitely.

If she squeezed his throat for a little while, then the noise would stop. She could sleep. Hours and hours of blissful, uninterrupted sleep.

Helen almost screamed herself. Had she really thought that? She covered the top of the baby's head with kisses, muttering, "I'm sorry. I'm sorry. Oh Ricky, sweetheart, I'm so sorry," as though he'd heard her murderous thoughts and understood them. Kisses couldn't drive away her guilt.

It swirled round her head along with her tears. She was a monster.

And if she strangled him it would be quiet.

My God, who was she?

Exhaustion.

Guilt.

This couldn't be real.

Mum yelled, "If you don't shut up, I'll put you out of the airlock!"

Ricky. The baby Mum was holding was called Ricky too. How odd.

Something snapped. Flesh and blood could only take so much. One handed, she flung towels out of a wall net. Then she gently put Ricky in the net and went into the airlock. She shut the door behind her, and the volume reduced considerably. Helen gave a long shuddering sigh. She could think - sort of. The crying still set her teeth on edge, but it didn't fill the universe any more.

What was that relaxation exercise they used to do at school? Helen shut her eyes, breathed in through her nose and out through her mouth. She pictured a tropical beach with waves gently lapping the silver sand. And a baby lying on the beach, screaming.

It was no good. She couldn't even manage a simple relaxation exercise. There was no way she could relax with that noise going on, even in the background. She took a spacesuit out of the rack and got in. Then she evacuated the airlock. She didn't need to open the outer doors; no air meant no sound.

Silence.

Beautiful, sumptuous silence. Helen stretched out in it like a cat.

It was wonderful.

Time to think.

In the memory - if it was a memory - Mum was huge. So if it was real, Helen would have been very young, about three. That would explain why she hadn't remembered any of it before. But it couldn't be a memory because she'd never had a brother. Unless the first Ricky died and they'd never told her.

She must have been mad to get pregnant. What on earth gave her the idea that she could be a better mother than her own mother had been? She'd wanted to murder a helpless child. Could she live with herself, knowing that?

She was a complete failure as a mother. She hated herself. And she didn't have to listen to that screaming any more.

She cried with exhaustion, guilt, and relief.

How long had she been out here? She'd better go see to that baby.

Helen refilled the airlock and got out of the suit. The crying had stopped.

She went back into the main living room, and found the silence unnerving. She dashed over to the wall net.

Ricky was asleep. He smelt of diaper.

She lifted him out and cradled him, drinking in the silence and the wonder of him. He pulled the strangest faces in his sleep. A sloping forehead like ET and a pointy crown to his head. Tiny clenched fists. Tiny arms that jerked out every few minutes, as though he dreamed of popping out into the big wide world.

She stroked the soft, fine, auburn curls. She marvelled anew at the umbilical stump, drying out already. Had she really thought of strangling the poor, helpless mite? A baby deserved a better mother than her. He had a little bruise on his nose from being born. She kissed it.

"Congratulations Helen," said the AI. "In spite of your childhood you passed the new parenthood exam with distinction. Unlimited breeding rights."

Ricky and the spaceship disappeared. She was back in the floatation tank. Wires slithered out of her scalp. It wasn't painful, but it was the tactile equivalent of chalk on blackboard.

The AI was still talking. "It took you seven hours to reach breaking point - most unusual - and even then you didn't have flashbacks or hurt the baby."

Flashbacks. Hurt the baby...

Mum towered over her, her face distorted into a Halloween mask. "Helen! WHAT HAVE YOU DONE WITH RICKY?"

Helen smiled. It would all be OK once she explained to Mum. "He wouldn't stop screaming, so I put him out of the airlock like you said."

Her mum screamed and screamed, just like Ricky.

The emotional earthquake shook great chunks of memory free that came crashing down on Helen like concrete blocks. She'd hated little Ricky. He'd taken her happy Mum and turned her into a tearful stranger. She'd longed for him to disappear.

And she'd murdered him. Shoved him out of the airlock like garbage. No wonder the doctors had insisted on full psychological testing. Dear God, how had the poor mite felt when the vacuum ripped the air from his lungs and he couldn't even scream any more?

She could hear screaming.

"Oh dear," said the AI. "You'd repressed it, hadn't you?"

Helen realised the screams ricocheting off the grey metal walls were her own, but she couldn't stop.

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