The House with the High Wall by Arthur Gask

A COUPLE of days later Robert was all prepared to set out for Bury St. Edmunds to try to locate these mysterious friends of the dead David O'Shane who had entrusted him with jewels of such great value to sell for them. Determined to ride in comfort this time, he had invested in a new bicycle and serviceable kitbag to strap upon the carrier.

The more he thought about his intended quest, the more and more certain he became that there was some very big secret to be found out, for why otherwise, he kept on asking himself, would the loss of so many thousands of pounds worth of jewels have been taken so tamely? If their hands were clean, the owners would surely have come forward at once and claimed the valuables, but with their continuing to hide themselves away, it must mean that for some very vital reason they dare not disclose themselves.