Exploring international literature often leads to fascinating discoveries. While '怪人二十面相' is originally a Japanese classic, several platforms offer English translations or summaries. Project Gutenberg might have older translations in public domain, though I couldn't find the exact version there last I checked. Some academic sites like JSTOR occasionally feature analysis papers that include plot summaries.
For contemporary readers, checking Amazon Kindle or Google Books could yield results - I remember seeing an English adaptation titled 'The Fiend with Twenty Faces' there before. It's worth noting that complete translations might be rare, but plot synopses frequently appear on wikis or fan sites dedicated to Japanese detective fiction. The nuance of Edogawa Rampo's style does get somewhat lost, but the core mystery remains captivating.