After the Storm, believed to be Tom Thomson's final artwork, set for auction

What's believed to be the final painting Tom Thomson completed before his mysterious death in July 1917 is poised for auction in Toronto this week.

In his final years, Thomson came into his own and created what would be considered the finest works of his career, including his iconic works The West Wind and The Jack Pine.

After the Storm, a late-spring oil sketch dominated by green foliage, stems from this fruitful period.It's a somewhat unusual work for Thomson, who was known for depicting autumn colours and helped inspire the legendary Canadian artcollectivethe Group of Seven.

"The 1916-1917 years were really where he hit his stride. We look at that painting today and it looks energetic, modern and lively. It looks like a modern landscape today and it's 100 years old," Robert Heffel, vice-president of HeffelFine Art Auction House,told CBC News.

"Because Thomson died so young, his paintings are so rare to the market," he added.

"There's some thought that this is the last painting he painted."

After the Storm is the final entry listed in Thomson's catalogue raisonne, the comprehensive, annotated listing of all known artworks by a particular artist.

Final days

On its reverse, After the Stormbears an inscription noting when it was created, scrawled by Thomson's patron Dr. James MacCallum, who had visited him in Algonquin Park earlier that year.

"The weather has been wet and cold all spring and the flies and mosquitoes much worse than I have seen them any year... This however is the second warm day we have had this year," the celebrated artist wrote to MacCallumin a letterdated July 7, 1917.

"Have done some guiding for fishing parties and will have some other trips this month and next with probably sketching in between," concluded Thomson, who was last seen alive the following day when he embarked on a canoe trip.

His body was discovered in the lake about a week later and, though accidental drowning was ruled the official cause of death, myriad theories aboundabout Thomson's demise.

After the Storm will be auctioned Thursday in Toronto as part of Heffel's fall sale, along with a trio of canvases by au courant Canadian icon Lawren Harris, pieces by international favourites such as Roy Lichtenstein and more.

Click on the video above for more highlights of Heffel's fall auction.