ok so at the very, very beginning, joel comes home from work and his preteen daughter, sarah, a blonde girl with a texas accent, gifts him a wristwatch.

she is then awoken by the commotion of the outbreak and you play as her and essentially walk downstairs where joel comes in through the glass door and gets his revolver. from there you drive to the city where there is a car crash and then sarah is shot and dies in joel’s arms.

when he wakes up several years later from a nightmare on the couch, you can see that he is still wearing the watch sarah gave him but the crystal is smashed and it doesnt work. through the game, the watch is shown from time to time representing the trauma of losing sarah and the transference of his feelings from sarah to ellie. at the hospital he calls ellie “baby girl” which is what he called sarah while she was dying in his arms. its kinda the driver of the plot