Sussex fought back after making a nightmare start to their County Championship match with Middlesex at Lord's.
Skipper Mike Yardy saw his side collapse to 33-4 and 66-5 after winning the toss and electing to bat.
But battling innings from Ed Joyce and Ben Brown saw Sussex recover to 242-8 at the close of day one in the division one encounter.
The day got off to the worst possible start for Sussex on what looked a decent batting wicket and favourable conditions.
Opener Chris Nash fell off the second ball when he edged a lifting delivery from Murtagh to the wicketkeeper.
Murtagh then struck twice in the space of four balls to dismiss Joe Gatting and Mike Goodwin, both caught in the slips, and when Yardy followed Sussex were reeling on 33-4.
Luke Wright and Joyce put a temporary halt to the carnage with a partnership of 33 before Wright played a loose shot to a delivery from Stephen Finn and was caught behind.
Joyce survived when Ollie Rayner was unable to hold on to a sharp chance at second slip to complete his half century.
He put on 81 with Brown before gloving a catch down the leg-side to the wicketkeeper having made 77 to give Finn his second wicket.
Brown and Naved Arif then added 63 for the seventh wicket before Finn ended Brown's inning with the new ball.
The players had just returned after a short rain delay and Brown's concentration seemed to be affected as he took a swipe at a wide ball and edged to Rayner at second slip for 70.
Arif followed for 38 when he tried to cut a ball from Murtagh (4-41) which was too close to him and picked out Gareth Berg at backward point.
Jimmy Anyon and Steve Magoffin were both on 11 when play was brought to a close after 92 overs.