The Devils eased into a six-point lead after only two races, but could not extend that advantage until Todd Kurtz and Steve Boxall managed a 5-1 against Thomas Jorgensen and Danny Gappmaier in heat nine.
Theo Pijper and Gappmaier pulled back a 5-1 for Berwick against Sam Simota and Boxall in heat 12, leaving the Devils with a four-point lead going into the final three races.
Points were shared in each of those heats, leaving Plymouth with a narrow victory while Berwick picked up a losing consolation point as some reward for their efforts.
Devils team manager Lee Trigger said: “It was good to get the win after two weeks off from having a home meeting.
“It was a solid team performance in which all six riders chipped in.”
There were double figure scores from skipper Kyle Newman, reserve Sam Simota and Todd Kurtz, while new signing Steve Boxall weighed in with four (paid six) points.
“Steve might have been a bit rusty but he looked pretty good and will have his equipment fully turned in for our track by the next meeting against Glasgow on Friday.”
Plymouth: Jack Holder 7+1 (4 rides), rider replacement for Stefan Nielsen, Steve Boxall 4+2 (5), Todd Kurtz 11+2 (5), Kyle Newman 12 (5). Reserves: Sam Simota 12+1 (7), Ellis Perks 1 (4).
Berwick: Kevin Doolan 5+2 (4), Dawid Stachyra 0 (3), Theo Pijper 8 (5), Matthew Wethers 8+2 (4), Thomas Jorgensen 12 (5). Reserves: Danny Gappmaier 4+1 (4), Liam Carr 6 (5).