Possible Clues:

• Is left behind with nothing at The Strand for Scarlet Pimpernel (4-1'-3-4)
• Ghostly light
• Marsh light
• Ignis fatuus
• White pillows can be something hard to get hold of
• (Treacherous) marsh light
• Elusive figure of bat is round the person's head
• Pale flame or phosphorescence - elusive thing
• Illusion that misleads
• Elusive goal