Medicine Lake is not actually a lake but an area in which the Maligne River backs up and suddenly disappears underground. During the summer months meltwater runoff fills the lake. It slowly drains through an underground river system . The underground system is extensive and tests during the 1970s made it clear that the underground system was one of the most extensive in the world. When traced by dyes it has taken anywhere from half a day to a week for the water to make the trip from Medicine Lake to Maligne Canyon, a distance of about ten miles. Even then, the dyes didn't show up at only one final destination. Dyes turned up in the Canyon, Lac Beauvert by Jasper Park Lodge and in several of the other lakes between.
Local tribes believed that the effect was due to evil spirits and magic, 'bad medicine', hence the name.
Wolves in the region have been known to chase caribou into the mud of the drained lake so they'll get stuck.