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The Light Within starred Olga Petrova (invariably billed as "Madame Petrova") as lady doctor Laura Carlisle. A dedicated bacteriologist, Dr. Laura discovers a cure for meningitis but runs out of funding before she can bring her discovery to practical fruition. To finance her experiments, the heroine marries wealthy Clinton Durand (Lumsden Hare) a cold and brutal man. Laura is actually in love with her assistant Dr. Leslie (Thomas Holding) but remains with Durand, not only because of his money but also out of concern for her young son Donald (Freddie Verdi). While struggling to stem an outbreak of meningitis, Laura discovers that Donald has died of pneumonia. To overcome her grief, she devotes all her energies to perfecting her cure for the outbreak, with selfless Dr. Leslie volunteering to act as guinea pig for the experimental serum. Alas, Durand, his mind unhinged by jealousy and by the death of his son, breaks into Laura's lab, smashes all her equipment, and destroys the serum vials. Racing against time, Laura manages to whip up a new batch of serum, saving the lives of Dr. Leslie and thousands of others -- while Durand, having exposed himself to meningitis, dies a slow and agonizing death. Ironically, The Light Within opened in February 1918, just before the deadly influenza epidemic which killed hundreds and thousands of North Americans.