Republic of Ireland Under-21 defender Dennehy joins from Cardiff while 20-year-old Plummer, who can operate on the wing or in an attacking role, joins from Bristol City. Both players have joined on initial one-month loan deals.
Fellow loanee Manchester United striker Febian Brandy, who scored two goals in nine appearances for the Priestfield outfit, has returned to Old Trafford with an ankle injury so will not feature.
Winger Andy Barcham, defender Garry Richards and goalkeeper Simon Royce are all out with knee injuries while Simon King and Danny Jackman are long-term absentees.
Source: Team Talk
Source: Team Talk