At Justiina's insistence, Pekka and Pätkä are looking for work again and end up starting a detective agency. The first assignment takes the duo on a cruise on Lake Saimaa. Traveling on the same ship are representative Johannes Kulo and his daughter Maija, as well as the lumberjack Jussi, who gets caught up in the duo's misadventures.

Esa Pakarinen
as Pekka Puupää

Masa Niemi
as Pätkä

Anja Hatakka
as Maija Kulo

Ami Lovén
as Jussi Leino

Siiri Angerkoski
as Justiina Puupää

Veikko Linna
as Johannes Kulo

Eino Kaipainen
as Leino (uncredited)

Juhani Kumpulainen
as Viljo Leino (uncredited)

Tauno Söder
as Rainer Strand (uncredited)

Armas Jokio
as Pikkarainen (uncredited)