[Show abstract][Hide abstract] ABSTRACT: We carried out a multi-wavelength study of a Coronal Mass Ejection (CME) and an associated flare occurring on 12 May 1997. We present a detailed investigation of magnetic-field variations in the NOAA Active Region 8038 which was observed on the Sun during 7--16 May 1997. This region was quiet and decaying and produced only very small flare activity during its disk passage. However, on 12 May 1997 it produced a CME and associated medium-size 1B/C1.3 flare. Detailed analyses of Hα filtergrams and MDI/SOHO magnetograms revealed continual but discrete surge activity, and emergence and cancellation of flux in this active region. The movie of these magnetograms revealed two important results that the major opposite polarities of pre-existing region as well as in the emerging flux region were approaching towards each other and moving magnetic features (MMF) were ejecting out from the major north polarity at a quasi-periodicity of about ten hrs during 10--13 May 1997. These activities were probably caused by the magnetic reconnection in the lower atmosphere driven by photospheric convergence motions, which were evident in magnetograms. The quantitative measurements of magnetic field variations such as magnetic flux, gradient, and sunspot rotation revealed that in this active region, free energy was slowly being stored in the corona. The slow low-layer magnetic reconnection may be responsible for the storage of magnetic free energy in the corona and the formation of a sigmoidal core field or a flux rope leading to the eventual 2 eruption. The occurrence of EUV brightenings in the sigmoidal core field prior to the rise of a flux rope suggests that the eruption was triggered by the inner tether-cutting reconnection, but not the external breakout reconnection. An impulsive acceleration revealed from fast separation of the Hα ribbons of the first 150 seconds suggests the CME accelerated in the inner corona, which is also in consistent with the temporal profile of the reconnection electric field. Based on observations and analysis we propose a qualitative model, and we conclude that the mass ejections, filament eruption, CME, and subsequent flare were connected with one another and should be regarded within the framework of a solar eruption.