The Palm Sunday Case was a series of events involving cross correspondence and numerous psychic mediums, over a long period and involving members of the American Society for Psychical Research (SPR). The case spanned more than 30 years and takes its name from the day one of the claimed communicators, Mary Catherine Lyttleton, died: Palm Sunday.
Mary Catherine Lyttleton died on March 21, 1875. When alive she fell in love with Arthur James Balfour in 1875, but fell ill and died on Palm Sunday, before Balfour could declare his intent. According to the SPR, in the next 30 years thousands of fragmentary messages from hundreds of mediums, when considered as a whole, seem to indicate Lyttleton was trying to communicate with Balfour, aided by members of the SPR Edmund Gurney, Henry Sidgwick and Frederic William Henry Myers.
Myers died in 1901, and various mediums were organised into concurrent sittings at locations very far apart, and notes were made of the words and phrases, and the automatic writings thus obtained. The messages were unintelligible individually and to individual mediums, but over a long period and many seances, it was claimed by the SPR that there was purpose in the correspondences, indicating an intelligent entity was behind them.