The Charity Shop Detective Agency by Peter Boland

Fiona, Sue and Daisy, three retired ladies who volunteer at the local charity shop, Dogs Need Nice Homes, can’t believe their favourite customer is dead. Eighty-six-year-old Sarah Brown was found murdered in her hallway by her delivery man, a domino clutched in her hand — with a name scratched on it. When another person is found dead with a domino in their hand, and with the police making no progress, the ladies will need to help unmask a serial killer. But at least they have Fiona’s scruffy-haired terrier cross to assist them. With plenty of tea and cake along the way, and despite squabbles with their rivals, the Cats Alliance across the street, the Charity Shop Detective Agency is born.