Every person who, having knowledge that any of the wrongs conspired to be done, and mentioned in section 1985 of this title, are about to be committed, and having power to prevent or aid in preventing the commission of the same, neglects or refuses so to do, if such wrongful act be committed, shall be liable to the party injured, or his legal representatives, for all damages caused by such wrongful act, which such person by reasonable diligence could have prevented; and such damages may be recovered in an action on the case; and any number of persons guilty of such wrongful neglect or refusal may be joined as defendants in the action; and if the death of any party be caused by any such wrongful act and neglect, the legal representatives of the deceased shall have such action therefor, and may recover not exceeding $5,000 damages therein, for the benefit of the widow of the deceased, if there be one, and if there be no widow, then for the benefit of the next of kin of the deceased.

But no action under the provisions of this section shall be sustained which is not commenced within one year after the cause of action has accrued.