[Normally, this might illicit some concern from bystanders, but the only person who seems to notice Derek grabbing Li-Na's arm is Li-Na herself. She turns around, a look of alarm on her face, as the rest of the commuters pass around them.]
Can I.... help you?
Other options:
no subject
[Normally, this might illicit some concern from bystanders, but the only person who seems to notice Derek grabbing Li-Na's arm is Li-Na herself. She turns around, a look of alarm on her face, as the rest of the commuters pass around them.]
Can I.... help you?