The Ramsay Street character is played by Ian Smith, whose return to the soap was confirmed in December.
His new stint in the show will see him comfort Toadie when he discovers the truth about Sonya Mitchell's connection to his adopted son Callum.
However, Harold - who returns with new fiancée Carolyn - will apparently find that not all of his help is received with the goodwill in which it is given.
Speaking of his return earlier this year, Smith said: "Harold is called back to Ramsay Street to help a friend... And of course there's human pathos, there's laughs - lots of laughs - [and] a little bit of romance."
The scenes will air in the UK on Channel 5 in June.