An altitude-triggered lightning flash with 8 leader/return stroke sequences containing 15 attempted leaders and 8 stroked leaders was observed with a high-speed camera and a mirrorless camera. The path and velocity characteristics of these leaders are investigated in detail. These leaders propagated along three different paths and had different development processes. Attempted leaders are found to die out in three ways: slow down and then disappear in somewhere of the path, give up propagating along the path and switch to propagate along the channel of a branch, be caught up and merged by other leaders propagating along the same path. Propagations of attempted leaders are not progressive, with some of them not always reaching as far as previous one did. The terminal height of attempted leaders ranges from over 1617m to 875m above the ground. A branching node is found to be the critical point determining a leader to attach the ground or not. Average 2-D speed of attempted leaders range from 2.7×105m/s to 21.0×105m/s. Some of attempted leaders even propagated in a higher speed than stroked leaders before they died out. There is no inevitable relation between the initial speed and their final fate. A critical value of propagation speed between attempted leaders and stroked leaders reported here is found to be 4×106m/s. Attempted leaders are found to slow down before propagating to the two branching nodes along the path.