In the beginning Svedberg mentions license plate numbers on cars leaving a ferry. The numbers he mentions consist of two letters and two digits, but Swedish license plates have three letters and three digits, which is the case with all the shown cars leaving the ferry.
Every other time Wallander enters a dangerous situation, he readies his weapon. However, in One Step Behind, as he enters his own home, almost certain that danger awaits himself or Linda, he does not. You can see in the close up of him holding his weapon, the hammer is resting in the safe position, and his weapon is unready, and incapable, of firing.