The woman was thin and bent with age and care, shivering in a heavy overcoat. Her left hand was held at an angle as if she was asking for something and her right foot jerked minutely every once in a while. For all that, she smiled and nodded at Jim's words, though Spock doubted she could tell, or cared, what they were.

Her name was Mabel. She was returning home from the market, having bought nothing.

Jim grinned and presented her an apple with a magician's flourish. She beamed and giggled.

The woman was dangerous.

Spock knew that from knowing his Captain's heart, so capable of empathy and pity. Sometimes it allowed him to leap ahead to truly Vulcanian conclusions which most humans shunned, fearing misery. If Jim made such a leap now...

But Mabel waved, limping slowly to a door, and Jim waved back and turned to him.

'Such a charming lady!'

'What will you have for lunch?'

'A bit of my own fat.'

'That,' said Spock severely, grasping at the safer topic, 'is not a healthy diet.'

'Okay, okay. I'll take one bite of yours. For the vitamins.'

'My fat is even less - '

'I meant your lunch.'

Sighing through his nose, Spock produced his own apple, weighed it, calculated its approximate nutritional value and measured up the bright-eyed human at his side. Jim was jumping up and down and rubbing his hands to keep warm. His hands... he had carried the woman's bag so that she could hide hers in her pockets.

The green light across the road now allowing their passage, Spock resumed walking.

'You will have the whole of it.'

'Will not.'

'Captain.'

'Exactly.'

'Very well!' he said in clipped tones, making Jim's eyes narrow in worry. 'Let us hurry; we are running late.'

And so they were. Perhaps they were already late, and McCoy had wrought the damage. It would be hard to detect, yet.

Stop, Spock chided himself silently. He really ought not to presume that McCoy wouldn't do something magnificently disastrous, especially as the man wasn't thinking clearly, so detecting could really be the easy part.

And he had no evidence to build predictions on, except - except the nature of the man and the nature of the age.

'Spock!'

Automatically, he turned his head to meet his friend's gaze and felt slight vertigo.

'You're awfully pink - what is it? Sit down! Have a sip.'

When the tepid water from Jim's flask touched his lips, Spock shook himself and sternly told his Captain to put his coat back on and let him rest a moment.

'You should go home!' the Captain said, clutching his sides and dancing in the cold.

'I am well enough to - .'

'The goal,' Jim countered heatedly, ''s not t' be able to work t'day and 'xpire t'morrow.'

'I agree,' said Spock, pushing himself up and bundling up the man in the too-thin garment. 'We are nearer to work than home, anyway.'

'Are y-you tr'ly 'll right?'

'Yes.'

'Race you.'

And Jim took off, and he took off after Jim. But even running, Spock thought.

The nature of McCoy was, without doubt, Humanity, bred by years of not standing by permitting suffering.

And the nature of the age...

He thought of the War that would come so soon - Mabel could live to see it - and the Wars that would come later, the ones human historians were still trying to comprehend back when Earth had entered the Federation of Planets.

He thought of other people like the woman, old at sixty and infirm, perhaps, from as early as fifty. Or was it forty? Hasn't there been a pandemic outbreak of a neuron-affecting virus about a decade before?*

Spock could re-invent a drug to help her, to help them all. McCoy's education, for all intents and purposes, was vastly inferior, but even so, the Doctor would be a godsend to the plagued population. AIDS. Breast cancer. Robotic prosthetics. He didn't have to know how to make everything from scratch - he just had to pass on everything he did know, there were enough skilled specialists to devise the rest, though it might take a while.

And Spock would have to stop McCoy from doing that.

For the sake of the Enterprise and innumerable other fates they had no right to alter.

For the sake of the Prime Directive, forever unknown to those who was most affected.

He dreaded to think what it would do to the Captain.

Though perhaps it would be something simple, resulting from reflex and not conscious thought; the Doctor was, after all, highly impulsive. Or it could even be a mistake. Like accidentally upsetting an apple-cart and helping a criminal escape and commit another murder. He would thank them for preventing that, and Jim's conscience would be significantly eased. The irony of it!

On the other hand, it could well be that they were to stay the Doctor's hand from a just and merciful action, in which case both he and Jim would rage against the duty of preserving Temporal Continuity.

But if Spock were to seek solace - which he didn't need, being a Vulcan - then he could at least count on neither human thinking about what they were leaving unchanged.

And he would not tell.

*encephalitis lethargica, of appr. 1916-1927, according to Oliver Sacks's 'Awakenings'.