You may wish to refer to a work that you haven't actually read, but which has been summarised in somebody else's work. This is known as secondary referencing. You should always try to track down the original work but, if this is not possible, and you must quote the ideas of one author which you have found in the work of another, your in-text citation must mention two names:
However, your bibliography should only give details of the source that you found it in (in this case, Walsh 2018).