‘That’d be the one.’ Niall gripped the boy tightly, pulled the offending implement from his pocket, and pushed him towards the car. ‘You’re coming with us, chum.’

As the teenager stepped forward, something slid from beneath his jacket and fell on to the pavement.

Yvonne picked the mask up with distaste. ‘Yours?’

The boy struggled to get free of Niall’s iron hold, and when he failed he threw her a baleful look. ‘Give it back, pig!’

‘Sorry, poppet. But even though it suits you far better than me, I think I’ll keep it. Now, get in the car! There’s a comfy little cell back at the nick, with your name on the door!’

‘Is everything against me right now?’ Nikki fumed. ‘Why the hell you had to come this way to get to the bloody University beats me!’

‘I’m not local,’ said Joseph reasonably. ‘It’s the only way I remember. And we couldn’t ignore an assistance call, now could we?’ With little or no effort, he frogmarched two youngsters towards a waiting police van.

‘I know that!’ Nikki dodged a flying missile, then wrestled a youth twice her size to the ground and knelt on him until a uniformed constable dragged him up and cuffed him. ‘But the timing stinks!’

Joseph had just relinquished his hold on his two charges and was making his way back to her, when she heard him call out.

‘Ma’am!’ Over there!’

She spun round and saw one boy rip a mask from the face of another, then turn tail and run from the brawling group. The boy who remained screamed and fell to the ground, blood oozing through his T-shirt. ‘Jesus! He’s been stabbed! Someone call a paramedic!’

Before she could get to the boy, two other officers were with him. ‘Help’s on the way!’ called someone, and Nikki turned to see Joseph hurtling after two youths, one who was still carrying the stolen mask.

‘Oh shit! That silly bastard’s going to get himself killed!’ She cursed under her breath, then raced after him.

The two boys fled down a narrow alley, one of their usual getaway routes, but found it blocked by a stationary delivery truck. Joseph and Nikki were on them in seconds.

‘Come here, you little turd!’ Nikki threw herself against the shorter of the two, the one who had stolen the mask, and slammed him roughly against a garage door. Air escaped from his lungs in a loud gasp, and she snapped her cuffs neatly around his wrists. Carefully, she slipped her hand into his pocket and withdrew a sticky-bladed flick knife. ‘Oh, you are so nicked.’

Holding him firmly, she turned to see Joseph lifting the taller boy from the gutter by his jacket collar.

‘You too, sunshine,’ said the sergeant brightly.

She exhaled loudly. ‘Let’s get these two scrotes back to the van, then—’