Jessica goes to London when she hears that her cousin Emma (also played by Angela Lansbury) has been killed.  When Jessica arrives in London, Jessica learns that Emma is not dead but instead in hiding after threats on her life.

You can stream the episode on Amazon with an IMDb account: https://www.amazon.com/gp/video/detail/B07NWL227H/ref=stream_3p_hd_ep?autoplay=1&t=0

Guest Stars include:
1. Patrick Macnee (The Avengers) as Oliver Trumbull
2. Glynis Johns (Mary Poppins) as Bridget O'Hara (Wardrobe
3. Olivia Hussey (Romeo and Juliet) as Kitty Trumbull
4. Barrie Ingham (The Day of the Jackal) as Inspector Roger Crimmins
5. Kristoffer Tabori (other Murder She Wrote episodes) as Ernest Fielding

Here is a link to the IMDb page: https://www.imdb.com/title/tt0653614/?ref_=fn_al_tt_6