The two of them followed the directions and the thin trail of smoke that wafted past the queue at the cash machine to find Susan slouched against a wall, cigarette between her fingers, leg crooked so one foot rested flat on the bricks. Her head was tipped back, smoke leaking from her lips, eyes closed in bliss.

Esther cast a revolted look at the enormous trash container right next to where Susan was standing and wondered whether students had to pass some kind of basic hygiene test before they made the Hippocratic oath. On current evidence, Susan would fail. “So, is this where he’s meeting us?” she asked.

“Him who?” Susan pushed her way off the wall and stubbed out her cigarette.

“The man,” Esther whispered, but her friends looked nonplussed. “You know. The one we’re seeing about a dog?”

“I wish we were seeing a man about a dog,” Daisy said wistfully. “Do you think there’s a black market for students who just want to pet a puppy for an hour?”

“Definitely.” Susan nodded.

“It’s a euphemism.” Esther tried again.

“No, I think Daisy really does want to pet puppies . . .”

“I do.”

“I MEAN THAT WE’RE HERE TO SCORE SOME DRUGS.”

There followed the sort of silence that only occurs when lots of people have heard something they shouldn’t, and Esther became acutely aware that the line of people waiting for the cash machine was peering at her from around the corner.

One of them, a middle-aged lady with a crutch in one hand and a cash card in the other said, “Aren’t we all, pet? Aren’t we all . . .”

The man in front of her nodded. “Came in here for some antibiotics, and now I’m waiting for a bloody X-ray.” Others in the queue murmured in sympathy. “I told them, it’s just a gammy foot. Google it, mate. All I need is a bit of penicillin.”

Next to her, Esther felt Susan tense, but with everyone distracted by comparing and contrasting Google diagnoses with the treatment they were waiting for, it was the perfect time for them to edge deeper into the shadows. As they did, an indistinct form emerged from behind one of the bins.

“Ptolemy,” the figure said.

“Walters.”

Their dealer was female, medium height, wearing office-style civilian clothing rather than the scrubs Esther had been expecting. Maybe thirty? As far as Esther was concerned, there were only five ages of human: child, her age, thirty, parent age, ghost.

“You got the goods?” Walters asked, and from the capacious pocket of her cable-knit cardigan, Susan produced a handful of small syringes still in their sealed bags.

Esther’s eyes widened in horror as Susan exchanged syringes for a single slim foil pack of pills. Before she had a chance to protest, to fling herself between the two and prevent Susan from enabling this poor woman’s addiction, the deal was done, and Walters was gone.