Fog
In the opening shot of the film, Scorsese composes the image of a ferry drifting out of the fog towards Ashecliffe. Scorsese uses fog to create a mysterious, gloomy atmosphere, one where events and motives are hidden and obscured from the viewer. Against the image of the obscuring fog, Scorsese later ties in the revelatory symbol of the "lighthouse."
Ward C
One of the first shots of Ashecliffe is a low shot of the towering Ward C, with electrified fences and double-fortified gates of entry. Ward C is a Civil War-era military fort whose interiors resemble a prison much more than a hospital. Within the Gothic horror conventions of Shutter Island, Ward C becomes a kind of haunted castle or haunted house that Teddy must navigate in order to find Andrew Laeddis.
Hushing woman
The glimpse Teddy catches of the older woman making a hushing gesture on his walk across Ashecliffe is a brief but powerful moment. The wordless exchange conveys the fact that Ashecliffe's patients have been instructed to remain silent and comply with Cawley's "radical, cutting-edge role-play," designed to break Teddy out of his delusions.
Rachel's ghost
Teddy is haunted by the vision of his dead daughter Rachel, who symbolizes his feelings of guilt. He first imagines seeing her body in a corpse pile at Dachau, where he served during World War II, before seeing her again in his first dream with the first Rachel Solando. He later sees her walk forward and take Dolores's hand before a vehicle explodes.
Guns
Teddy's gun helps Scorsese show whether or not he might be a violent or sane man. Teddy resists handing over his firearm to McPherson at the beginning of the film, and Chuck's improper holstering of his gun almost gives Cawley's entire performative experiment away early. Teddy only learns at the end of the film that his gun has been a plastic toy the entire time.
