There had been a conversation, near the end of their partnership, discussing the eventuality of Steed inducting someone else in to his mad world.
He had warned Cathy, in that irritatingly patronising way he could shrug on and off like a garment, that it would be best if she had nothing to do with any potential replacement; she had retorted that once she left she would never even want to see his face again.
After he left her flat, she regretted saying that. It wasn't true, not really: John Steed simply had a knack for getting under her skin, and it was a sensation she didn't entirely care for.
But inevitably, their partnership drew to a natural end and she found herself back doing what she loved.
No thoughts of Steed and the next poor innocent he'd dragged in to his affairs.
But she was an inquisitive woman, not as repulsed by working with Steed as he probably thought, and as the months passed she began to wonder. In the end it was easy to folow him a couple of times, to find a flat number and street, and to get the name of the person inside.
Mrs Emma Peel.
Another widow, she thought wryly.
And so, one day when she was sure that Steed was elsewhere, Cathy Gale rang the doorbell to Mrs Peel's
"Hello," the woman said, half wary and half intrigued. "Are you looking for me?"
"Then yes, I am looking for you." Cathy paused, eyeing the woman up and down. Brunette, petite but obviously in shape, and with humour in her eyes. Yes, Steed had chosen infuriatingly well. "I believe we have a common acquaintance. Overly fond of umbrellas and bowler hats, and likes to call himself a gentleman."
Interest appeared in Emma's eyes. "How do you know him?"
"We used to work together. Devious criminals, mad scientists - I think you're well acquainted with the type."
"You'd better come in."
Closing the door behind her, Cathy glanced round the flat. It was tastefully decorated, if not quite in the style of a young lady, judging by the fencing equipment on the table. "Mrs Peel," she began.
"It would be best if you didn't tell Steed about my visit."
"Oh?" An inquisitive look was directed at her.
"I was warned away from you," she admitted. "I have no idea why. Perhaps he's worried I'll tell you things he'd rather you didn't know."
"And are there many of those?"
Cathy hesitated. "What do you think of him?"
"Brilliant and devious. I should say he was fun to work with, as well."
She raised an eyebrow. "Fun? Well, perhaps he's changed."
Emma laughed, and it was a beautiful sound. "He talks about you sometimes."
"I can't imagine why. We didn't have the warmest of relationships."
"Perhaps," she said ambiguously. "So...what are these forbidden topics he's so frightened you'll talk about?"
It had been her plan to warn the beautiful young widow about Steed, to tell her about all the times he had let her down or made callous decisions. But in the flesh, Mrs Emma Peel was all softness and strength, and there was a trusting light in her eyes when she spoke about her partner.
Cathy didn't want to destroy that. Trust was precious, not easily found and even less easily retained.
"I'm not sure, really," she said eventually. "But would you like to go for lunch?"
At Emma's smile, Cathy thanked Steed silently for the first time in months. This could be the beginning of something wonderful.