Continuity mistake: When Gertie and Joey make their escape running down the stairs of the hall, they pass by a couple (she has a white hat and a blue dress). When Poirot and Japp run after them, the same couple has jumped back several meters. (00:43:00)
Abra Cadaver - S3-E4
Visible crew/equipment: At the beginning of the episode, when the brothers chat around the central morgue table, the boom mike appears above the table, on the upper side of the screen. (00:04:55)