There may – controversially – be no duty to rescue at common law (see, eg, Alan Calnan (SSRN), David Hyman (pdf)), but the emergency can beget the man (Wagner v International Railway 232 NY 176 (1926) (Cardozo J)), even in New York. However, although danger may very well invite rescue (Wagner (Cardozo J) again), nevertheless, it seems that it would now be wise to decline the invitation in California. From Ratio Juris:

… The California Supreme Court has given fresh meaning to “no good deed goes unpunished.” It ruled last week that a woman who yanked a co-worker from a crashed car four years ago, and may have made her injuries worse, can be sued because what she did wasn’t medical care. …

The best conceptual discussions are EJ Weinrib “The Case for a Duty to Rescue” (1980) 90 Yale Law Journal 247 and the very different WM Landes and RA Posner “Salvors, Finders, Good Samaritans and other Rescuers: An economic study of Law and Altruism” (1978) Journal of Legal Studies 83 (SSRN); for Irish law on the point, see “Danger Invites Rescue. The Tort of Negligence and the Rescue Principle” (1992) 14 Dublin University Law Journal 65.

Why do I have the urge to hum the Dionne Warwick/Burt Bacharach/Hal David song “Walk on by“?