As the U.S.S. Discovery crew attempts to let loose at a party, an unwelcome visitor comes aboard bringing about a problematic and twisted sequence of events.

Sonequa Martin-Green (Specialist Michael Burnham)
Doug Jones (Commander Saru)
Shazad Latif (Lt. Ash Tyler)
Anthony Rapp (Lt. Paul Stamets)
Mary Wiseman (Cadet Sylvia Tilly)
Jason Isaacs (Captain Gabriel Lorca)

Wilson Cruz (Dr. Hugh Culber)
Katherine Barrell (Stella Grimes)
Peter MacNeill (Barron Grimes)
Rainn Wilson (Harcourt Fenton "Harry" Mudd)

Milton Barnes (Deck Crew #1)
Emily Coutts (Lt. Keyla Detmer)
Jason Deline (Medical Officer)
Hamza Fouad (Deck Crew #2)
Julianne Grossman (Discovery Computer)
Patrick Kwok-Choon (Lt. Gen Rhys)
Sara Mitich (Lt. Cmdr. Airiam)
Oyin Oladejo (Lt. Joann Owosekun)
Ronnie Rowe Jr. (Lt. Ronald Bryce)
Izaak Smith (Jogger #1)

• Harry Mudd uses a time crystal to trap Discovery in a 30-minute time loop in order to take over the ship to deliver it to the Klingons. Because of his connection with the spore network and the tardigrade DNA, Lt. Stamets is the only one who remembers what happened in each loop.
  
• This episode does not contain an opening act. It goes from the Previously on Star Trek: Discovery sequence directly into the title sequence. ("Encounter At Farpoint" was previously the only Trek episode that did not feature an opening act.)
  
• Burnham and Tyler share their first kiss in one of the loops, though neither of them remember it.
  
• The stardate given in this episode doesn't fall in line with the previous and subsequent stardates. (Perhaps it was mistakenly given as 2136.8 instead of 1236.8)