ORIGINAL AIRDATE: May 15th, 1989 ---
A villain from MacGyver's past is back to finish the job, but which one?
MISSION: MacGyver, Pete and Jack spend some time panning for gold in the wilderness when they are beset upon by a baddie from MacGyver's past. Can they identify the attacker before they are all taken prisoner?
This week's highlights include:

Keep your ears peeled toward the end for a cameo from my darling daughter.

Speed of sound (Physics)

The speed of sound is the distance traveled per unit time by a sound wave propagating through an elastic medium. In dry air at 20 °C (68 °F), the speed of sound is 343.2 metres per second (1,126 ft/s; 1,236 km/h; 768 mph; 667 kn), or a kilometre in 2.914 s or a mile in 4.689 s.

Check out the article on wikipedia: https://en.wikipedia.org/wiki/Speed_of_sound.

Watch S4E19: "Unfinished Business" on CBS's website or check the alternative streamability of this episode here.