There’s a perfect storm brewing in “The Block Island Sound,” but it’s not in the skies, as you might suspect from its setting on the coast of Rhode Island. After their sly debut “Funeral Kings,” the one thing that can be expected from brothers Kevin and Matthew McManus is the unexpected and while the opening shot of their latest is ominous, picturing a rudderless boat on the water without seemingly any passengers onboard, it is actually more unsettling to discover there is indeed one in Tom (Neville Archambault), lying face down and gradually waking up from what can be assumed to be a heavy night of drinking or a possible bout of dementia, as it’s surmised when he’s reeled in by his son Harry (Chris Sheffield).

It would be unwise to arrive at any hasty conclusions when the McManus Brothers cleverly leave a lot of room throughout “The Block Island Sound” for uncertainty to fester, particularly in regards to Harry, who is quick to dismiss the conspiracy rants of a friend (Jim Cummings) about vaccines developed from parasite extract, yet is increasingly susceptible to theories about the craziness that’s going on around him. Dead fish have been piling up 9 to 10 tons at a time at West Beach and Tom, who can be caught staring in a trance at times and simply disappears on his boat at others, has become increasingly unmanageable, a burden Harry shouldered willingly when his mother died, but has become resentful of when his two sisters have been able to largely be free of such responsibilities. One, Audrey (Michaela McManus), returns not necessarily to see her dad, but to investigate the fish situation for the EPA.

Given the current climate situation, the McManus Brothers make the most out of a ripe time for a paranoid thriller where the temperature on the pot rises so incrementally that you don’t realize it’s boiling over, and with a guide like Harry, who starts to worry he’s going down the same path as his father, experiencing blackouts and other mental miscues, the coincidence of a potential sea change geographically with the one going on inside his own head becomes fertile territory for a tale that tosses and turns like a beached fish washed ashore, but is anything but floundering. Sleek where their first feature was scrappy, the brothers handle a slippery narrative with great skill as Harry’s trust deteriorates in others when his anger towards those who haven’t been there for him in the past begins to rear its ugly head, but also when in himself when he can no longer believe what he’s seeing at times.

The top-notch production values across the board, from Sheffield and Michaela McManus’ assured performances to cinematographer Alan Gwizdowski’s ever-tightening framing, serve a wonderfully subversive purpose in providing some level of comfort while largely distracting from the diseased thing going on inside of “The Block Island Sound” until it can no longer be ignored, culminating in a wild finale that’s as well-reasoned as it is surprising. Although “The Block Island Sound” offers no escape for its characters, it proves to be a pretty fine one for everyone else.

“The Block Island Sound” will screen once more at Fantasia Fest on September 1st at 11:10 pm EST virtually for Canadian residents.