about
midnight
`` I had an idea they might have doubled on their tracks for a time , and backed her up just to fool us , '' Tom said . `` They might do that , keeping her in the same tracks . '' But this , evidently , had not been done , and the tank was making good speed away from the Swift house . They kept up the search until about midnight , and then a heavy rain began just before they reached a point where several roads branched . `` Luck 's with them ! '' exclaimed Tom . `` This will wash away the marks , and we 'll have to go it blind .