The 4th row. At each choice of square, the leader says ‘OK’ or ‘BOMB’ and if it’s OK, they proceed to the next choice of square. If it’s BOMB, the next member takes a turn trying to get further than the last contestant. Leader makes out a set of grid patterns (about 5) and uses a different one each time. Each grid has to be successfully negotiated before the next set is used. Points are given each time the grid is negotiated successfully.