Du Plessis exited for 52, pulling Jimmy Neesham to Trent Boult at deep square leg with less than four overs left in the session. He constructed a recovery which Bavuma built into dominance.
The crowd swarmed to the fence in joy as du Plessis strode off, but were ushered away by security. Perhaps they were breaching health and safety regulations?
The most nervous man at the venue was presumably Mike Davies, a groundsman in his maiden test. His pitch struggled for bounce and carry initially - B-J Watling took a few deliveries around his boots - but the sun baked it enough to have the ball humming through the afternoon. Given the early scrutiny of his olive rectangle, Davies must have been tempted to put his feet up late, or perhaps do a jig within the confines of his shed.
Strike bowler Trent Boult led the way for the hosts with one for 44 from 22 overs. He conceded eight runs from a nine-over opening spell which included the lbw of Stephen Cook. His role, pitching up and regularly convincing the batsmen to play and miss, was crucial in the absence of Tim Southee. Southee missed on the basis of selection rather than injury or illness for the first time since New Zealand played India at Hyderabad in August 2012.
Boult was also backed up by fellow left-armer Neil Wagner's two for 59 from 20. He has only played club games since fracturing a finger on his bowling hand. Wagner capitalised on Hashim Amla's lack of foot movement by getting a ball through his defence. He then got a short-pitched delivery to brush Jean-Paul Duminy's glove and helmet grille, ballooning a catch to Ross Taylor.
The logic of Southee's omission was presumably that Wagner would do more work off the wicket than Southee would in the air across the course of the test. However, it restricted New Zealand's chances of swinging the first or second new balls.
Southee made way for off spinner Jeetan Patel who joined the left-arm orthodox Mitchell Santner.
The last time New Zealand played two spinners at home was when Patel and Daniel Vettori teamed up against Australia at Hamilton in March 2010.
The hosts have won four consecutive tests this home summer, winning 2-0 against Pakistan and Bangladesh. History also looms as an incentive against an opponent they have never beaten in a series, despite 15 attempts across 85 years.
Conversely, South Africa have won three consecutive rubbers since August against New Zealand, Australia and Sri Lanka under their new skipper.
Morne Morkel returned from a long-standing back injury to make the South African XI at the expense of Duanne Olivier. Spinner Keshav Maharaj came in for Wayne Parnell.
