When the passed pawn has advanced beyond Bähr's border line, the defender draws: he gives up the blockade at the right moment, takes the pawn and runs back to c8.
Push the white passed pawn one square further than in the previous lesson (e6 instead of e5, with the kings moved up correspondingly) and the verdict changes. The pawn on e6 is beyond Bähr's border line (a5–b6–c7 then c7–d6–e5–f4–g3–h2), so the position is a draw with correct defence. You are Black, to move.