Perhaps the most significant, and most certainly most widely reported, of the ghosts is that of a young woman who haunts the north wing and the panelled corridor between the Hall of Meredith and the Great Chamber. In the nineteenth century the room behind the panelling was called the 'Ghost Room'. A white or grey woman was said to have been frequently seen in the room and the adjoining passageway, accompanied by a foul smell of putrefaction. Whilst the apparition has not specifically been seen in recent years, its presence continues to be felt and some have claimed to have been touched on the shoulder whilst at the same time experiencing a considerable drop in temperature. In addition, the extraordinary smell associated with the sightings continues to be experienced, always in the same part of the passageway.

Sir John Wynn, first Baronet

Whilst we are not certain of the ghost's identity, an account published in 1906 provides a vivid (and rather horrific) explanation for the sightings and their associated smell. Apparently Sir John Wynn (either the first or fifth baronet - this remains unclear) seduced a serving maid at Gwydir in his youth. When the relationship became…complicated, the unscrupulous Sir John murdered the girl and had her body walled-up within a large void in one of the chimney breasts. The smell of the decomposing body, it is said, lingered for months as an unfortunate reminder of his former amour. Significantly, a hollowed-out space was found earlier this century within the large chimney breast which backs onto the Ghost Room at the hall end of the passage. This, long called the 'priest hole', is where the body was said to have been secreted; and it is in this area that the smell is always at its strongest.

The fifth baronet is said to have made a deathbed confession to a murder committed at Gwydir during his youth in the mid seventeenth century. But the first baronet (1553-1627) is an equally likely candidate for the girl's murder. His (much-exaggerated) reputation as a local tyrant was established already in folklore when Thomas Pennant, the antiquary, visited the area in the 1770's. He recounts a tradition (which continues to this day) that the spirit of the old baronet remains trapped beneath the waterfall near Betws-y-Coed called the Swallow Falls, 'forever to be purged, purified and spat upon (by the waters) for the evil deeds committed by him in his days of nature'.

Sir John himself ranks amongst the many other reported ghosts. He has been sighted on a number of occasions on the spiral staircase leading from the Solar Hall to the Great Chamber; his portrait hangs in the Lower Hall. A detailed account of all the other sightings would prove exhaustive, but amongst them children have been heard crying, a Ghost Dog has frequently been seen (incredibly, its bones were unearthed in the cellar in 1995), and a procession has been seen at night on the Great Terrace, near Sir John's arch.