Kill Clock by Allan Guthrie
Gordon Pearce is a nice enough sort of guy. Just as long as you don't get on his wrong side.
One evening while he's taking his dog for a stroll, a double-crossing ex-girlfriend turns up out of the blue with a couple of scruffy toddlers and a tall tale involving loan sharks, death threats and something called a 'kill clock'. She begs Pearce for help. Claims he's her last resort. But he's convinced she's trying another one of her cons. Last time he saw her, she fleeced him good and proper, and he's not going to let that happen again.
But as the night goes on, doubts start to creep in. Problem is, Pearce can't afford to believe her. Because if she's telling the truth, he has until midnight to rustle up twenty grand in cash or he'll have another death on his conscience.