The Irwin Case

"Guests at Doveby House don’t usually pay by credit card, but when one tries and his card is refused, Janet Markham can’t help but wonder if there’s something more going on than a simple glitch in the credit card machine.
As more stories of troublesome cards spread through Doveby Dale, Janet gets more curious, but unexpected guests keep her too busy to do much. As she and Joan work on clearing out the carriage house, a new mystery presents itself.
Can Janet work out what links the credit card cases together?"7