You can add The Uncertain: Last Quiet Day to your steam game account for free. This promotion is available for a limited time and it requires just adding the game to your account on Steam during the promo window (June 5th to June 9th)

The Uncertain is an episodic story-driven adventure game set in a post-apocalyptic world. Experience the mysterious vibe of each of carefully explored locations, solve diverse puzzles, make fateful decisions and discuss intriguing matters to find out the whole truth being kept from you. The Uncertain: Last Quiet Day has Mostly Positive reviews on Steam and it usually costs $14.99

Just head over to Steam or navigate to the game in Steam Client before June 9th 2020, add the game to your cart and checkout. Simple as that. After that, the game is yours to keep, and play, forever.