Honor told her that it was and the girl said, ‘Maybe it’s a sign then,’ and turning to Nevis and holding out her hand, added, ‘I’m Satnam. I hope we both get in so we can be friends.’ Which was the best thing any stranger had ever said to Nevis before or since.

At the second floor, Nevis switches her phone to silent. Swiping in to the library, she makes her way directly to her usual seat – K14 – and accessing her coursework, a mathematical model of the movement of seawater in deep ocean vents, due at the end of the week, on her phone, begins to check the equations. She won’t make the deadline. Her tutor on that project is Dr Ratner who has seemed cool about other students’ late submissions, though she supposes she’ll have to run it by him.

For the next hour or so she does her best to focus. Before long, her mind is toggling between Satnam and Honor. Eventually even those worlds blur and her eyelids give in to the gravitational pull.

She wakes, some time later, disorientated and anxious. Inside her a bird still flutters its blue metallic wings, the remnant of a recurring dream, then fades. The bird is Alcedo atthis, one of the world’s 114 species of kingfisher, and her favourite of all the water birds. In the Bible kingfishers are the first animals to leave the Ark after the flood. In Greek mythology they are Alcyone and Ceyx, a pair of star-crossed lovers who are punished by the gods before winning their pity. For as long as she can recall the birds have appeared in the watery realm of her dreams.

She lifts her head from her arms. Sitting opposite is Daniel something or other, a student she hardly knows, who catches her eye and makes a sad-emoji face. A moment later an email notification appears on her screen via the university’s intranet. Is Satnam going to die? Daniel xoxo.

It’s only been a few hours since the incident on the bridge and the gossip mill is already churning. Wanting no part of it, Nevis is rising and gathering her things to leave when there comes a tap on her shoulder and she turns to see a tall woman, about her age, with straightened dark-brown hair and too much make-up.

‘It’s Tash,’ the girl says in response to Nevis’s blank expression.

Nevis searches her mind. The name Natasha Tillotson pops up. One of the girls in the Valentine’s photograph on Satnam’s feed. Something odd about that photograph, though her mind can’t quite organise itself to work out what. The expression on Satnam’s face?

‘What happened?’

‘I don’t know.’ Tash blocks her way, her face darkening. Nevis protests but still Tash does not move.

‘You were there on the bridge, weren’t you? That’s what everyone’s saying.’