The Black Mountain by Rex Stout

In this gripping mystery, the astute detective Nero Wolfe and his loyal assistant Archie Goodwin embark on a perilous journey to the Balkans after the murder of Wolfe's childhood friend. As they navigate the treacherous political landscape of post-war Montenegro, Wolfe is driven by a personal vendetta, determined to uncover the truth behind the assassination. The duo faces a web of intrigue, danger, and deception, testing their wits and resilience in a foreign land where allies are scarce and enemies lurk in the shadows. Their quest for justice leads to a dramatic confrontation, revealing the complexities of loyalty and revenge.