Hell in the Undercroft: Demon Summoning Beneath St Vincent’s Chapel at Edinburgh Fringe

The Essentials

1. 1

   An unruly teen is replaced by a polite demon in this high-energy pop-punk musical comedy at the Edinburgh Fringe.
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   Experience the irony of dark rituals unfolding in the shadowy stone undercroft beneath an active historic chapel.
3. 3

   Discover why exhausted parents prefer a helpful hellspawn over their own rebellious son in this hilarious show.

Wasatch Theatre Company is staging Possessive! The Musical! at The Undercroft at St Vincent’s Chapel for the Edinburgh Festival Fringe 2026. Running in the intimate basement beneath an active Scottish Episcopal sanctuary, the production turns suburban occultism and demonic possession into a high-energy pop-punk musical comedy.

The production centres on an accidental demonic pact in the 2000s USA, but its venue adds a delightful stroke of irony. While prayers and liturgical services continue in the sanctuary above, audiences step down into the stone undercroft beneath Circus Lane to watch dark rituals, cultists, and devilish agreements unfold.

A Consecrated Refuge: The History of St Vincent’s Chapel

Sitting at the intersection of St Vincent Street and picturesque Circus Lane, on the border between Edinburgh’s Georgian New Town and Stockbridge, St Vincent’s Chapel is a 19th-century Gothic gem. Designed by Liverpool architects John, William, and James Hay, the church opened its doors in 1857 as a village place of worship in the heart of the city.

The building holds a curious history rooted in chivalric lore. Between 1967 and 1996, St Vincent’s served as the Collegiate Church of the Grand Commandery of Lochore of the Military and Hospitaller Order of St Lazarus of Jerusalem. Heraldic banners, crests, and armorial shields from the Order still decorate the interior above. Below the floorboards, the Undercroft spans the entire footprint of the church. While it houses the congregation’s church music library and community events during the year, August transforms the subterranean stone space into a Fringe venue where ancient ritual tropes meet modern musical theatre.

The Review: Possessive! The Musical!

Written by Spencer Ford, Possessive! The Musical! takes place in Swarthmore, Pennsylvania, at the turn of the millennium. The plot follows Carl and Hannah, two exhausted suburban parents struggling with their unruly teenage son and their rebellious goth daughter, Lisa. When Lisa’s DIY occult ritual goes sideways, she unwittingly summons a commanding master demon who commandeers her brother’s body, accompanied by a chaotic, incorporeal minion.

The comedy flips classic horror conventions upside down. Rather than terrorising the household, the invading demon proves remarkably polite, well-mannered, and tidy… a vast improvement over the rude teenager who previously inhabited the bedroom. Faced with the choice between an unruly son and a helpful hellspawn, the parents decide that postponing the exorcism might just make family life easier.

The staging uses a clever physical trick to sell the possession. While the possessed son lip-syncs on stage, a costumed demon performer stands just behind the set scenery to project the real vocals live. The six-person cast maintains a brisk, sharp rhythm, supported by a live keyboard player seated right behind the crowd. Both parent characters bring sharp comedic timing to their roles as long-suffering suburbanites, and the interplay between the demon and his unruly lackey delivers consistent laughs across the two-hour runtime.

Possessive! The Musical! balances suburban domestic parody with sharp songwriting and supernatural farce. Staged in the shadowy basement of a historic chapel, it makes for a spirited, eccentric hour of Fringe entertainment.