Consultant series producer Justin Young recently told Digital Spy that the programme's team are making plans for another one-off edition which will take Holby away from the UK.
Marcel has now expressed excitement over the upcoming special, which comes following the success of last year's Christmas episode in Ukraine.
Asked what is coming up for Jac, the actress told Inside Soap: "An amazing standalone episode set in a foreign country - but that's all I can say!"
Marcel spoke to the magazine to campaign for votes ahead of next month's Inside Soap Awards. Holby City has been nominated for 'Best Drama' alongside Casualty and Waterloo Road.
Discussing the show's chances, she added: "We've never won, and we get five million viewers every week. It's boring when awards go to the same shows every year - so I'll flash the crowd if we win!"
The Inside Soap Awards take place in London on September 24.