‘Oh, yeah.’ Halliday unzipped her bag and pulled out another plain black one. She handed it to Sellers. ‘The Two fucking Sisters. Of course, the one who fights for good causes and isn’t totally frivolous turns out to be the killer. Men have to demonise women who attempt any kind of serious work. And you honestly think Billy might not be a man?’ She walked away, laughing.

Silently, Sellers made a vow: he would solve the murder of Joshua Norbury if it was the last thing he did on this earth. He knew it was wrong of him to care more about Norbury than about Billy’s other victims simply because of his sex, but, thanks to Sondra Halliday, he did.

He pulled his phone out of his pocket and scrolled down the contacts list until he got to Lisa Norbury, Josh’s sister. No, he wasn’t going to check in with Waterhouse or anyone else first. For once, he was going to follow his own instincts.

Arriving at the McElwee Winery’s large, half-empty car park on a sprawling, grey industrial estate, Charlie was disproportionately delighted to spot Nikhil Gulati’s car straight away. There it is! she thought. Everything’s coming together!

The comedown was fast. Of course his car was here. He worked here and it was a weekday. This couldn’t be notched up as a new gain. Still, Gulati might easily have been abroad on a business trip or at a meeting out of the office, so Charlie allowed herself to count the presence of his Skoda as a good omen. It made speaking to him a possibility, assuming that was what she decided to do.

She’d spent most of the drive from Spilling to Linton trying to manufacture a reason for needing to interview Nikhil Gulati that had nothing to do with her sister. She’d considered asking him about his relationship with Philip Sier, and a few questions about Sier and his wife Emily.

Charlie had her police ID with her, though she’d nipped home to change out of her uniform, so she could compel Nikhil to talk if she chose to. He was unlikely to refuse on account of her not being with Cambridgeshire Police, though he might want to ring Spilling nick before agreeing to be questioned.

Even if he didn’t, it was a risky approach to take: if word got back to Culver Valley Police that Charlie had used her police status in the service of a personal obsession, she’d lose her job. Also, it would be massively unfair to Nikhil Gulati and Philip Sier, who might both suffer unnecessary anxiety as a result.