Heath Ledger (left) and Christopher Plummer
Bryan Bedder/Getty Images; Gretchen Walker/Everett Collection
01/28/2008 AT 03:30 PM EST
Director Terry Gilliam is feverishly working to figure out how to keep Heath Ledger
alive on film, according to one of the late actor's costars in The Imaginarium of Doctor Parnassus
, which Ledger was still shooting when he died last week.
"Terry's throwing himself into the job of trying to salvage the picture," veteran actor Christopher Plummer told PEOPLE over the weekend.
Despite earlier reports that the director might shelve the $30 million production, Gilliam, whom Plummer describes as "terribly saddened" by Ledger’s death is "trying to work out at this moment how to continue on. Fortunately, because the film deals with magic, there is a way, perhaps, of turning Heath into other people and then, using stills and I think they call it CGI…
"Terry was a very good friend [of Heath's]," adds Plummer. "He very wants to go on with the movie, and I can very much understand why. Because he wants to dedicate it to Heath, of course."
Ledger and Plummer both left the London portion of the movie's shoot last weekend and were due to continue filming next week in Vancouver. Leaving England, says Plummer, "Heath was in very high spirits. He was just enjoying himself tremendously. It's a rather fanciful script, and he was wonderful in this role."
Confirming earlier reports that Ledger hadnt been feeling well on set, Plummer says, "we all caught colds because we were shooting outside on horrible, damp nights. But Heath's went on and I don't think he dealt with it immediately with the antibiotics.…I think what he did have was the walking pneumonia."
On top of that, "He was saying all the time, 'dammit, I can't sleep'…and he was taking all these pills [to help him]."
As well as the damp cold and lack of sleep, Plummer describes the shoot as rigorous. "We had to shoot every second we were out there…there was hardly any time to go into the tent or the car to keep warm. We just kept shooting…boom, boom, boom…there was no pause. It was very, very hard work."
Ledger would have appreciated the show-must-go-on mentality, says his co-star. "He was terribly likeable and obviously enormously talented…and the combination was terrific. It's such a shame these things have to happen to the good ones."
As for reports that Gilliam has approached Johnny Depp to step into Ledger's role, the actor's rep tells PEOPLE: "There have been no official talks, and he is currently working on Public Enemies
for Michael Mann for Universal."