he had tried to concentrate on the job in hand , to block out distractions of home and work , to focus his energies on the task of spotting minute clues on the ground and in the undergrowth that might just provide the give-away clue to the presence of a large , out-of-place feline in the neighbourhood , but each time he set about his pursuit he was consumed by the futility of the activity , and could not help but allow his mind to wander to thoughts of his wife : of their past ; of her present ; of his future .