Near the end of the film, Lara gets trapped in quicksand while trying to find water for Lupin. When he hears her scream, he completely forgets his illness and charges to her rescue. Lara tells Lupin there's nothing he can do and blames herself for not being mindful of the desert sands.
Despite this, he tries his damndest to save her; going so far as to strip down to his underwear to fashion a rope out of his clothing and tosses it to her. And just when it seemed it might work, the knot slips and Lara sinks deeper into the sand. As Lupin bemoans himself for failing, she tells him he's done enough and that he should go on without her. All she asks is that he help her people. When he continues to insist on trying to save her, she forcefullyyells at him to go away and leave her alone.