"How do you know qat?" Joan asked.
Sherlock was striding along, mouth set, eyes searching the street. At last he spotted what he sought - a cop car, parked. He leaned in through the window. "Excuse me. Could you give this to Captain Gregson from Sherlock Holmes? I've written his details on the bottom of the cup. Thanks - and don't spill it, it's vital evidence. Thanks."
And he was off again, darting through the crowds with Joan hurrying after him as the sky clouded over and it began to rain.
"Qat is widely used by the Somali and Ethiopian communities in London," Sherlock explained as they boarded a train to a suburb Joan had barely heard of. "It's a plant, the leaves of which can be chewed very slowly to produce a kind of high. Experts say the effects vary between chilled out relaxation, or manic babbling. There's a strong link between usage and marriage breakdown, also suicide."
They found seats and Joan noticed how Sherlock, at ease anywhere, immediately stretched out his legs and folded his arms, tilting his head back to expound at the grubby ceiling.
"It's not actually illegal in Britain, though it's heading that way. If you sit outside a cafe on the Roman Road in Bethnal Green, it won't be long before you're asked for it or offered it." He paused. "But it's very illegal here. Naughty Mr Bissell."
"Ok," said Joan, "so what are the Bissells doing with it?"
Sherlock sighed. "The original congregation of that church had a contingent of immigrants from Ethiopia and Somalia. Ethiopia is a big Christian country, Somalia less so. I guess Bissell encountered qat use and thought of a way he could turn it to his advantage. Because, you see, recent immigrants rarely have much insight into the financial systems of their new country. And church congregations are often made up of older, sometimes vulnerable people.
"Bissell got qat and put it in a herbal tea for his congregation. Whether they recognised it, as our umbrella retailer friend did, or not, still it's a drug which helps people let their guard down. And when they were feeling very trusting, Mr Bissell offered to help them with any money problems they might have. The people told me at the fire that he had totally looked after them since their spouses died, managing pensions, state allowances, even advising on property matters."
"Don't tell me " said Joan. "He wasn't doing this for love."
"Definitely for profit. And the Bissells don't own that delightful penthouse. The church does. They sold it to the church at a nice above market price, and lease it back. I imagine that it's next on the arson hit list. "
The train rattled on, the tracks raised above factories and houses. Joan looked down into oil storage depots and scruffy back yards. "Where are we going?" she asked.
"To meet the imaginary boyfriend and stop Cara Bissell in her latest mission of righteousness."
xxxx