Producers made the same decision not to preview episodes in series three when Lady Sybil was killed off and when Matthew Crawley exited in the Christmas special.
The opening two episodes of series four have featured both upstairs and downstairs at Downton slowly recovering from the loss of Matthew Crawley.
However, speculation is rife online that another major character might have been killed off by Julian Fellowes in a new twist for the hugely popular ITV drama series.
Further speculation about a possible dramatic twist in this week's episode has been sparked by the arrival of Nigel Harman's character Green.
Harman has claimed that his valet character has "no redeeming qualities" and said previously that he will "stir things up" in the period drama.
Fans suspect that Green will be involved in some fresh troubles for Bates and Anna, who actors Joanne Froggatt and Brendan Coyle have promised will face some serious troubles during the series.
Other arrivals in the latest episode include a new possible suitor for Lady Mary, Tom Cullen's Lord Gillingham, Andrew Alexander's Sir John Bullock and Kiri Te Kanawa as Dame Nellie Melba.
Meanwhile, another new character, Patrick Kennedy's Mr Sampson, is billed by ITV as "a slightly mysterious acquaintance from Robert's gentleman's club".
The latest episode will centre around an extravagant house party at the Abbey, held to raise spirits and cheer up Lady Mary.
Downton Abbey continues on Sunday nights at 9pm on Sunday.
Watch the stars of Downton Abbey talk to Digital Spy about season four: