This lecture describes the investigation of large and damaging settlements in the One Lombard Building in San Francisco Calif. The cause of the settlements was a mystery. Although it was known that settlement began during construction of a major new sewer near the building, it was not clear how the settlements could be related to the sewer construction activities. The paper explains the cause of the settlements and describes the technique used to remedy the problem. The legal and insurance aspects of the case, in some ways more mysterious than the technical aspects, are also described.Key words: settlement, foundations, clay, dewatering, pile driving, underpinning.