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Route 405 begins at an intersection with Route 1 directly across the from . The highway heads northwestward through rural areas, paralleling the Crabbes River, to pass through St. Fintan's, where it makes a sharp left at an intersection with a local road leading to St. David's and . Route 405 now heads southwest to cross the and pass through Loch Leven to turn north and parallel the Highlands River for several kilometres. The highway makes another sharp left as it begins following the coastline and passes through Highlands. Provincial maintenance for Route 405 ends at the southern tip of the community, with the road continuing southward for several kilometres as a gravel road.