she wondered whether this was the way tarquinius was feeling when he talked about the owls how one thing led to another , one death necessitated another , and though you 'd taken the first step for a good reason , or good enough , anyway , before long you found yourself tied up in knots of the logic of necessity ; like treading on stepping stones into the middle of the stream , where you found , at last , only one stone you could possibly step on , and it was a long stride , a slippery rock , a footing that might tip under you , and yet you had to take the step , and hope it was secure .