Restatement 324 – Duty of One who Takes Charge of Another who is Helpless
One who, being under no duty to do so, takes charge of another, who is helpless adequately to aid or protect himself is subject to liability to the other for any bodily harm caused to him by
a. The failure of the actor to exercise reasonable care, to secure the safety of the other while within the actor’s charge OR
b. The actor’s discontinuing his aid or protection if by doing so he leaves the other in a worse position than when the actor took charge of him