The magnetic cloud and geomagnetic storm on January 10--11, 1997 were associated with a halo-type Coronal Mass Ejection (CME) observed by the SOHO/LASCO coronagraphs near the sun on January 6. We summarize the solar activity related to this CME and the subsequent storm at Earth. This solar activity was remarkably weak and unimpressive. If the wide CME had not been observed, the storm would not have been forecast. Thus this case represents an extreme example of so-called problem magnetic storms that lack obvious surface signatures of eruptive solar activity. It supports the view that CMEs involve the destabilization of large-scale coronal structures which may or may not have associated surface activity, and that CMEs, not the surface activity, are the key causal link between solar eruptions and space weather at Earth. ¿ 1998 American Geophysical Union