The result means SA take a 2-1 lead into the sixth and final Test, which takes place at 6.30pm at Hartleyvale Monday.
Du Plessis, on the left baseline, beat her marker in the most confined of spaces and flicked high into the net from a near-impossible angle for the most breathtaking of goals.
It was yet another nerve-jangling match that mirrored the earlier encounters. The first two Tests were drawn 1-1 and 3-3 before SA won the third international 3-2 only for Belgium to win the fourth clash by the same 3-2 margin.
Belgium stars Jill Boon and Anouk Raes celebrated their 200th Test caps and in the second minute Judith Vandermeiren cut inside from the right and the play led to keeper Sanani Mangisa making a great save.
A penalty corner ensued and Bernie Coston made a superb stop and cleared the danger after ace goalscorer Stephanie de Groof fired off a trademark low bullet. Taking on the defenders, Belgium had the early edge. Anne-Sophie Wayans cut in unchallenged from the right and Mangisa was on hand to make an intervention before pulling off a stunning reflex save moments later.
SA had their moments on attack but were not connecting enough passes together. Du Plessis’ goal in the 10th minute suggested the tide was turning but in the 12th Mangisa pulled off a magnificent stick save to her right from a De Groof rocket that left the PC goal-machine in utter amazement. A further Mangisa stop ensured SA went into the second chukka a goal to the good.
SA skipper for the day Jade Mayne was working tirelessly amongst the forwards and a Dirkie Chamberlain one-two saw final receiver Shelley Russell come agonisingly close to scoring, the awkward position of the ball denying South Africa’s attacking right midfielder.
In the 22nd centre midfielder Illse Davids broke through the middle and fed Sulette Damons out right, the SA striker’s full-blooded shot flashing past the far post. It was the Davids/Damons combination once again that saw the striker come so very close to adding a goal but it was not to be.
Looking at the bigger picture of putting together the ideal squad for the World League Semi-Finals in Valencia, Spain in June, SA brought on substitute keeper Hanli Hattingh for Mangisa after the half-time break.
In the 42nd minute Hattingh made two good saves, the second shot a delicate deflection effort from Boon. The SA defenders, well marshalled by Lisa Deetlefs and Nicolene Terblanche, continued to hold firm, while the forwards and midfielders also played a vital role in preventing a Belgium equaliser in the third chukka.
One minute into the fourth and final chukka of 15 minutes, Mayne’s grit won a PC but Belgium survived. SA camped in the Belgian defensive third for seven minutes, Mayne and Chamberlain - so strong on the ball when challenged - playing a prominent role, but the two-goal cushion didn’t come.
Belgium eventually broke out to win a PC and De Groof acted as a decoy, Anne-Sophie Scheemaekere taking the shot but Hattingh’s feet were well set to make a top save.
Both sides had their chances in a thrilling last five minutes and SA defender Christine Roos made two courageous blocks to prevent Belgian goalshots. At the other end a number of good opportunities came SA’s way but in the final analysis Du Plessis’ 10th minute winner in another exciting Test match was enough.
Investec SA: Sanani Mangisa (GK), Erin Hunter, Lisa Deetlefs, Nicole Walraven, Nicolene Terblanche, Shelley Russell, Bernie Coston, Jade Mayne (capt), Lilian du Plessis, Sulette Damons, Candice Manuel. Rolling subs: Hanli Hattingh (GK), Christine Roos, Illse Davids, Line Malan, Dirkie Chamberlain, Tanya Britz, Tiffany Jones.
Belgium: Aisling D’Hooghe (GK), Anne-Sophie Scheemaekere, Louise Cavenaile, Stephanie de Groof, Anouk Raes, Judith Vandermeiren, Lieselotte van Lindt (capt), Emilie Sinia, Barbara Nelen, Jill Boon, Joanne Peeters. Rolling subs: Megane Simons (GK), Emma Pervez, Caroline Struijk, Anne-Sophie Weyns, Stephanie van den Borre, Manon Simons, Caroline Wagemans.
Umpires: Lyndal Robertson, Andrea Nicholson.
Monday – Sixth Test: SA vs Belgium (6.30pm at Hartleyvale)
Tickets: R30. Gates open an hour before.