Although Misfits isn't a thriller we could still use it as an influence for our thriller opening.
In this specific scene they have used various close ups of the knotted hands, his face covered by the bag and his chest area to create a convincing "strangling". I thought we could perhaps use these ideas if its too hard to kill somebody with a plastic bag alone, we could consider the idea of the girls hands being tied together. Perhaps she could wake up, after having been knocked out, tied up in a room where she is then strangled. However this idea would make it difficult for us to include the thugs.