The Irish actor will appear opposite Gabriel Byrne in forthcoming detective serial Quirke later in 2013.
[Above: Colin Morgan as the title character in 'Merlin']
The role will mark Morgan's first television appearance since popular fantasy drama Merlin concluded on December 24, pulling in 7.8 million viewers.
The three-part Quirke will star award-winning Byrne as the title character - a sombre Dublin pathologist who solves crimes in the 1950s.
[Above: Gabriel Byrne filming 'Quirke' in Ireland]
Morgan will appear in the third episode - titled 'Elegy' - as the character Jimmy Minor. In addition to his Merlin stint, the 27-year-old has previously appeared in an episode of Doctor Who and in the 2010 film Parked.
Quirke has been filming on location in Ireland since November.
> Merlin review: Our verdict on the final episode
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