“Okay, Diane. Let’s see if we can start again. Our victim is named Gregor Franks, and there’s a possibility that he is the father of the child. Let’s assume that Leonie is the child’s real first name. Can we try searching for the name Leonie Franks on the Social Services database? And maybe Constance Franks? Also, this address?” She gave Diane a piece of paper with Gregor’s address on it. Then she turned to Atkinson. “Can you …”

He was already opening his laptop. “I’ll search for the names Leonie and Constance Douglas on the police database, boss, right away.”

A few minutes later, they had each drawn a blank.

“So. Constance Douglas doesn’t appear on the Social Services database. Nor Constance Franks, nor Leonie Douglas or Leonie Franks.”

Jo had to assume from now on that all the names were false. They were looking for an invisible mother and an invisible child.

“But she seemed so normal,” said Diane. “She seemed so—and I know this sounds terrible—but she was middle class. I don’t see many like that. Very nice, you know?”

Jo squinted at Diane. The woman had lost all sense of perspective. She wouldn’t be surprised if this case led to an internal investigation by the service, and even this person’s suspension. That might not be such a bad thing for the vulnerable children of Grimsby. Diane could do with a rest, at the very least. She had the word burnout written all over her.

“There’s one more thing we need you to help us with. I have a CCTV image of Constance in Sheffield train station on her way to Cleethorpes. Then the cameras catch her again leaving the Cleethorpes station, but we can’t find her returning or getting on a train. She certainly never came back to Sheffield. We need to know where she went.”

“That doesn’t make any sense. I know there’s a camera opposite the entrance.”

“We didn’t pick her up after she got off the train at Cleethorpes.”

“So, she never got on the train? She’s still in Cleethorpes?”

“Possibly. Or she was covering her face when she went past the cameras. I’ve got an officer scouring the footage at the moment, but it’s a slow process. Here’s the image we have of her.”

She showed Diane the image on the police tablet. There was the woman, her hood pulled up, dark hair showing. Those haunted eyes. Diane’s face creased in confusion.

“That’s not her. That’s not the woman I spoke to. I knew it. I knew there had to be a mix-up.”

“That’s not Constance?”

“No. The woman I talked to wasn’t as thin. She had different hair. Let me see it again.”

Harper watched as, if it were possible, even more color drained from Diane’s face.

“Oh no. How can that …”

“What is it?”