on the trail 追踪；追猎；寻找；跟随 They are hot (或 hard) on the trail of the three thugs. 他们紧紧跟踪这3名暴徒。 The lawyer is on the trail of new proof in the case. 律师在寻找案情的新证据。 trail off (或 away) 逐渐减弱；缩小 His voice trailed off into a whisper. 他的声音越来越轻，变成了耳语。 Her interest in the work trailed off. 她对这项工作的兴趣逐渐减退。