The image has a shoe and the word 'BACK' on it. Perhaps it means 'step back' (in time).
The text is a series of numbers followed by numbers in German. If we use the classic a=1, b=2... we get the following text:
Times 13There are two more hints in the source page: one at the end of the first part, and another one at the very end of the html. The second hint suggests the solution is a scientific term.
Pat 4 (this one is hidden).
The title is also a hint.
The words are all titles from past riddles, and the numbers in German are an index into the captions. The five resultant values yield an anagram that recalls a famous philosopher back in time. The hints in the HTML source suggest the answer is the means through which the 'duty' was accomplished. The solution is one word, lower case, but it's in Latin! Think botanical.